Obedience to God is a hard concept for many atheists to grasp. Many of them claim it's horrifying that Christians say they would obey anything God commands. Why? Because allegedly, if God commands them to do something evil, they would. Here's the problem: God can't command us to do something evil (James 1:13-14). In fact, everything God has ever commanded a Christian to do can be found in the Bible, which actually makes Christians fairly predictable. When the Bible says "thou shalt", Christians will, and if it says "thou shalt not", Christians won't. Obviously, this is not always the case. Christians vary in faith, maturity, and education, and we're still human, so we still struggle with sin. But ultimately, Christians obey the Bible, so unless we go rogue, you can predict our behavior just by knowing what Scripture says.
But does such a book exist for atheists? Absolutely not. There is no such thing as an atheist Scripture. There are no books or letters that all atheists everywhere universally agree is the infallible word of God, and this leads to a variety of different opinions among atheists. Ultimately, if you're going to claim you don't bow to any authority, and would even disobey God if you believed in Him (which ultimately you're doing whether you believe in Him or not, because He still exists), you're actually saying you are the unpredictable one.
As a human being, my natural inclination is to ensure the only people who have reason to fear me are those who give me a reason to fear them. And by that, I don't mean "anyone I don't like", I mean those who genuinely seek to harm me, or others around me. As a Christian, I seek to refine my natural inclinations by comparing them to the word of God. Ultimately, if a Christian can live in peace with you, we must live in peace with you (Romans 12:18). The only reasons to fear a Christian, therefore, is if A) he isn't following his faith, B) he doesn't understand his faith enough to follow it or C) you want to harm that Christian or someone in his/her care.
But what about an atheist? Turns out, there are lots of reasons to fear them. For starters, although many of them certainly are good people (by earthly standards), not all of them are. Atheism doesn't even have a rule against deception, so even if an atheist appears good, it's entirely possible that he is doing so as an attempt at self-preservation, or a con. While atheists say they fear Christians because we would do evil in the non-existent scenario that God told us to, an atheist can do actual evil simply because he wants to, even if God is against it.
The point of this article is not to demonise atheists. Rather, it is to defend against a semi-common attempt by atheists to demonise Christians. If you're an atheist, you are perfectly capable of being a good person. Romans 2:14-15 even tells us that God has "written the law on your heart", so all it really takes is for you to obey your God-given conscience and you probably will be a good person. But in the end, it's not good enough to be good. Right now, your own conscience ought to tell you you're not good enough to stand before God. You don't need to fear Christians, but the thought of standing before our God should terrify you. This isn't because He is evil, or unpredictable, but because you yourself are evil, and He is very predictable in how He deals with sin.
A time will come, hopefully later rather than sooner, when you will leave this life behind. You will die, and you will stand before God, and He will examine everything you've ever done, everything you've ever said, and everything you've ever thought. He will find every evil deed, every evil word and every evil thought, and He will judge you for it. That is terrible news, because even the very best of us have fallen short (Romans 3:23). So where would you go if, God forbid, you were to die before you finish reading this article? The Bible describes a harsh judgement. For sure, there are degrees of punishment (Matthew 10:15; Matthew 11:22-24; Mark 6:11; Luke 10:12-14; Luke 12:47-48), but no one under judgement will be comforted by the knowledge that someone worse than they are is receiving a worse punishment.
But there is good news. A punishment is due for all sin, but not all sinners receive it themselves. A worthy substitute can take their place, and a worthy substitute did. 2,000 years ago, Jesus came to Earth to be born as a human, and during His entire life, He did not sin. He deserved no punishment of His own, and yet He received one. He was crucified, and on that cross, He took the full wrath of God on your behalf. All you have to do to be forgiven of your sins is turn to Him in faith and repent. You can do that right now. You don't even need to finish reading, you can just pray, and I guarantee that if you ask with the right motives, He will answer.