As Christians, we believe God is beyond reproach, and that the Bible, being His word, is infallible. A common problem, however, is that Christians do not always act that way. Often, we have our own, worldly views, and this leads us to question Scripture, even to the point of bashing more faithful or knowledgeable believers. "If belief X is true, then conclusion Y".
An example of this is "if God sends people to Hell for all eternity, He is not a just God. Therefore, we must conclude Hell is a temporary thing". This is problematic reasoning because the starting assumption is worldly, not Biblical. Annihilationism, by contrast, is a philosophy based on the worldly assumption that an eternal Hell does not fit "finite" crimes. We could turn back by pointing out philosophical holes in the theory. For example, if a temporary Hell is truly sufficient to pay one's sin debt, surely the sinner should therefore be released, rather than annihilated, either through re-incarnation, or simply entering Heaven "the long way round"?
But pitting philosophy against philosophy ends up being a game of rock, paper, scissors. Only one thing beats human error consistently and reliably: The infallible Scriptures. Therefore, we can point out that the assumption is flawed. Whether we believe, as fallible sinners who of course have motive to suggest the punishment due to us is unfair, that Hell is unfair or not, the Bible says it is fair, and unfortunately, it is the fate that awaits the devil, his angels, and impenitent sinners. The only real ambiguity is the specific features it has. Is it a literal fire? Is it literally a lake? What exactly does "outer darkness" mean? Because Scripture does tell us Hell is a real, everlasting place, we have no business saying its existence would make God unfair.
The flip side of this, however, is that, to quote Mike Winger, "Scripture is sufficient, that doesn't mean that I am sufficient". God's perfection is not transferable, and thus even when we study His perfect word with all due diligence, it is inevitable we will run into error. The scary thing is, when we have done that due diligence, we can often sincerely believe our errors are Biblical truths. Thus, when we hear an attack on our philosophy, we hear it as an attack on God Himself.
I can think of no greater example of this than Calvinism. It takes a lot of love for Scripture to be a sincere Calvinist, and while I believe it is an erroneous philosophy, I simply cannot bring myself to count it as a heresy. Nevertheless, there are numerous flaws in Calvinism that come not from worldly assumptions, but Biblical facts.
For example, does God want all men to be saved? 1 Timothy 2:4 is one of several verses that tells us yes, He does. In fact, this is the very reason we are to make supplications, prayers, intercessions, and even give thanks for all men. No amount of twisting, reinterpreting, or even changing this Scripture, can change the fact that it plainly tells us God does want all people to be saved and come to the knowledge of the truth. This completely rules out Limited Atonement, and Irresistible Grace, in particular. Another example is the fact that God does not show favoritism (Galatians 2:6), and yet He would have to in order to so actively determine whether a man will choose salvation or not.
The key to understanding the difference is how explicit Scripture is in support of a given philosophy. In the case of Annihilationism, as discussed above, there is no Scriptural support, either for the philosophy as a whole, nor for the reasoning behind it. It is an entirely worldly philosophy, based on man's hatred for the idea of suffering eternally, as well as our low understanding of, and respect for, God's Holiness. Hell, by contrast, is explicitly taught. But as I briefly showed, while it can be said that Calvinism has some Biblical support, Scripture can also be shown to conflict with it in several ways. If Calvinism was true, we would have to bring human assumptions against it, just as we have to bring human assumptions against Hell. Instead, Calvinism is an incomplete philosophy, and can therefore be refuted not with human assumptions, but with Holy writ.
It all comes down to the distinction between God and our understanding of Him. Sadly, on this side of the Kingdom, none of us will ever have a perfect understanding of Him. Because of this, there is a difference between criticising something like Calvinism, and criticising God Himself.
Though Annihilationism and Calvinism are the examples I have chosen for this article, the principles I have described extend far beyond them. In fact, without saying what it is, I have an entirely different scenario in mind, wherein a sister in Christ publicly advocated leaving a church, not for an actual theological error or grave sin, but for a "doubtful disputation" (see Romans 14). Yet, all of the Scriptures she cited in her post were general condemnations of evil, not a contextual condemnation of the "sin" she was speaking against. The failure to distinguish between God and our understanding of Him, therefore, can actually cause division where there ought not be division. If we are to remain united as a Church and come to know God, it is vital that we stick to His word, letting the clear interpret the unclear, and showing patience even when sincere error arises.