One benefit of basing your theology on the word of God is that you need to make very minimal alterations to the word of God. Obviously, it's not as simple as running around citing the word of God and you can have everyone understand what you believe. The doctrine of the Trinity, for example, is 100% Biblical, but the Bible does not explicitly say "God is Triune". Therefore, you cannot run around quoting a Bible verse that says "God is Triune".
Sometimes, however, you can cite a Bible verse as if it is your own words to describe your doctrine. In fact, the words of the scripture in question are so clear that you can say it out loud without saying "this is what the scriptures say", and even the hardest of heretics knows what it means. But then you take them to the Bible and show them where, word for word, it says what you just said, and suddenly it conveniently doesn't mean what you think it means. Let's look at a few examples of this concept, which I call "the silent quote".
Creationism
As an ex-Evolutionist, Creationism is a particularly precious doctrine to me. Evolution is the religion I converted from, Creationism is the first consistent doctrine I formed, and I have spent more time researching and defending Creationism than any other theological issue. Creationism is explicit, almost to the excess, throughout scripture. Indeed, it would be impossible for any literate person to read the first 8 pages of a Bible, in any language, and believe it was presenting any other worldview. I once even sarcastically presented Genesis 1 as if my favorite theologian had written a case against Old Earth Creationism.
But aside from that, most Creationists will simply state their belief as "God created the heavens and the earth in 6 days". And everyone knows what that means. Why, then, do they struggle so much to understand God when He says "For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day: wherefore the Lord blessed the sabbath day, and hallowed it" (Exodus 20:11)?
When a Creationist says "For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day", we mean in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day, and everyone knows it, even the most stubborn of Theistic Evolutionists. In the same way, when the Bible says "...in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day..." it means in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day. Therefore, if Old Earth Creationists and the like know what it means when we say it, they should repent and affirm it with us.
Sola Fide
One strong evidence of the silent quote concept is the fact that it doesn't really work for other worldviews. Works based "gospels", for example, can be defended with a twist of scripture, but never with explicit statements. But that doesn't stop heretics from trying. For them, James 2:24 is a very popular verse, as it says "Ye see then how that by works a man is justified, and not by faith only." It's easy to see how this might trip up anyone who doesn't know the distinction between salvation and justification, or the context of James 2 in general. However, those with an understanding of Sola Fide are as comfortable affirming every statement in the book of James, without alteration or reinterpretation, as every other Biblical statement.
This includes Ephesians 2:8-10. Ephesians 2:8-10 tells us "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast. For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them." This passage exemplifies the silent quote concept, as it can be used quite proficiently by the weakest of amateur Bible students.
One popular YouTube pastor, Mike "Bible Thinker" Winger, tells of a time when he did this very thing with one of his Catholic friends. He cited the verse, and the Catholic said "that would be scary if it was in the Bible". So Mike showed him exactly where it is in the Bible, and the Catholic switched tactic: "I don't think that means what you think it means". Notice, when Mike said it, the Catholic knew exactly what it meant, and said it would be scary if it was Biblical. When shown it was Biblical, he conveniently lost his ability to understand it. This isn't because the meaning is somehow not obvious, but because he, as a Catholic, is not allowed to interpret the Bible according to what it says if what it says goes against the teachings of the Catholic Church. But the fact that what it says does go against the Catholic Church should instead convince him to repent and leave it.
Unlimited Atonement
Of all of Calvinism's 5 points, Limited Atonement is the least Biblically defensible. Not only is it indefensible in that it is literally never stated explicitly or implicitly, but there are also a number of implicit and explicit statements telling us that God "...will have all men to be saved, and to come unto the knowledge of the truth." (1 Timothy 2:4).
No translation I can find decreases the scope of 1 Timothy 2:4. Formal equivalence, dynamic equivalence, optimal equivalence, no method of translation has produced a reputable Bible version that renders 1 Timothy 2:4 as "all kinds" of men. Yet, Calvinists not only insist on this particular interpretation, but even suggest changing the Bible itself to state this.
When non-Calvinists cite verses that are not consistent with Calvinism, Calvinists know what the non-Calvinist means. Only when the scriptures are presented as scripture do Calvinists suddenly start reinterpreting them. But why bother with the reinterpretation? Why not simply admit that the issue of how man's responsibility and God's sovereignty relate to each other is not as simplistic as Calvinism makes it?
Monotheism
Monotheism is the most obvious feature of Christianity. If you know anything about Christianity, you know that we believe in one God. Why? Because scripture quite explicitly states that before God there was no God formed, neither shall there be after Him. These are the slightly edited words of Isaiah 43:10. But what did I edit? Did I remove context, like "some people say before God there was no god formed..."? No. Did I change the number of gods in the past, while the original says "before God there was another god formed..."? No. Did I change the number of gods that may be formed, while the original says "...but there shall be after Him"? No.
What I changed was the speaker. In the original verse, it is God Himself speaking. "Ye are my witnesses, saith the Lord, and my servant whom I have chosen: that ye may know and believe me, and understand that I am he: before me there was no God formed, neither shall there be after me." (Emphasis mine). Obviously, I can't say "before me there was no God formed, neither shall there be after me", because I am not the Lord, so I had to change the verse to come from my mouth, lest it be immediately obvious that I am employing the silent quote strategy. But the change does not affect the context in the slightest, it still means the identical thing.
Why, then, do Mormons continue to believe that not only was there an infinite string of gods before God, but that by being good Mormons, we can become gods? Obviously, it is not because they are somehow compelled by reason or scripture to interpret Isaiah 43:10 differently, because whenever Isaiah 43:10 is cited indirectly, they know what it means. By the same reasoning, they should know what it means when it is cited directly, and become Christians instead.
Prophesying Christ
And at last, we come to such a powerful example that even those who do not even have enough faith in God to become heretics ought to become faithful Christians. Throughout the Old Testament, there are many prophecies of Christ. Literally hundreds. But few of them compare to Isaiah 53, which is so powerful that if you take it to someone with only a cursory knowledge of the Christian faith and ask "who is this talking about?", they immediately say Jesus. Yet, Isaiah died nearly 700 years before Jesus was born.
It's interesting that this particular prophecy even works with devout Jews. Countless accounts can be heard of them rejecting the words of Isaiah 53 because "we don't believe the New Testament", or accusing Christians of having edited the scriptures. Any number of excuses can be made, and indeed are made, for why Jesus appears in Isaiah 53, but the most obvious answer is that He's meant to be there.
The question is, if you know it's Jesus when you think we're reading from the New Testament, how can you not know it's Jesus when you find out we're reading from the Old? "Because He isn't our Messiah!" Well, Isaiah 53 says otherwise. "Because prophecy is impossible". Then how did a prophecy of Jesus appear in Isaiah 53? Jew, atheist, some other form of weird and wacky religion, it doesn't matter who you are, you are almost certainly going to recognise Jesus in Isaiah 53, especially if you don't know where it's from when it's read aloud to you. But when you know where it's from, there are only two possibilities: Acknowledge that yes, that is Jesus, or stick your fingers in your ears and sing Ging Gang Goo.
Conclusion
Clearly, the Bible is quite capable of expressing itself, and so followers of its Author are capable of using it to defend their positions. Heretics, not so much. While they recognise the meaning of scripture when it comes from the mouths of the faithful, they aren't so capable of understanding it when it's still on the page. This phenomenon shows two things:
1. The Bible is clear. Certainly more so than certain heretics would have you believe. To them, it's open to interpretation (so of course their interpretation is right), or it's too ambiguous (so it clearly supports them). But the reality is that it's quite perspicuous.
2. Heretics know it until they don't want to know it. Heresy and false religions are held not for intellectual reasons, but for heartfelt reasons. Those with a love for God and a heart for the truth will, even if gradually, repent and submit to His word. But often, heretics would rather invent a host of excuses just to defend their beloved worldview.
But are they worth defending? In the case of things like Calvinism, it probably won't matter much. Calvinism is neither heretical (though it is wrong), nor will it cost salvation. But heresies like Mormonism are not worth the condemnation they bring. You may be able to tell me you think you'll be a god one day, and I have no authority to repay you for such blasphemy. God, however, does. If you walk up to Him and demand to become a god, your fate will be no better than when Satan tried the same thing. The wisest thing a man can do is to cease with all the nonsense and just listen to what God says. Doing otherwise leads to folly at best, eternal damnation at worst.