Earlier today a friend and I were talking about things in Christianity that tend to bother me. One of those things was the mantra of "atheists worship Satan." It drives me crazy because first off, they don't believe in neither God nor Satan. An illustration: a husband and a wife get into an argument. I'm on neither side and want them to have things sorted out. I point out a good point the wife has in the argument. However, that doesn't make me automatically on her side.
My friend pointed out a verse that states something like unbelief and other factors mean that the person is automatically against God, which really seems more like a false accusation that God is throwing out. My friend told me when a person doesn't believe in God, God is still going to take that as being against, which really doesn't make any sense since God is all-knowing.
"He who is not with Me is against Me, and he who does not gather with Me scatters abroad" (Matthew 12:30).
Your view only works if truth was relative and not an absolute. If multiple, contradictory things can all be correct, then you would have a point. But the problem is that truth, by its very definition is exclusive. There can be many untruths because falsehoods are contradictory, but there can only be one truth.
It is because of this that following, the following of truth, is then narrow, while all other paths are many. "Enter by the narrow gate; for wide is the gate and broad is the way that leads to destruction, and there are many who go in by it. Because narrow is the gate and difficult is the way which leads to life, and there are few who find it" (Matthew 7:13-14). As Jesus said, "I am the way, the truth, and the life. No one comes to the Father except through Me" (John 14:6).
You illustration of the husband and wife argument is not the same because the husband could be right, the wife could be right or neither are right. Your illustration has three states, which is not the same as truth.
So what about the atheists who claim to stand on the sidelines and not get involved? Let me illustrate it with laziness. "He who is slothful in his work is a brother to him who is a great destroyer" (Proverbs 18:9). Suppose you own a house. You can work on it, you can take a sledgehammer to it, or you can just let it go. But a house falls apart when it is not being actively maintained. Thus the non-participating path is really just a slower form of the destructive path.
The same is true in spiritual matters. You can actively work for righteousness, you can actively work for wickedness, or you can claim to stand on the sidelines. But without active effort, righteousness does not exists; therefore, being on the sidelines is a form of promoting wickedness. "He who is not with Me is against Me, and he who does not gather with Me scatters" (Luke 11:23).
Do atheist worship Satan? No, they don't believe Satan exists. However, their neutrality causes them to further Satan's goals. It doesn't take active participation in wickedness to help Satan, all it takes non-participation in righteousness. "Therefore, my beloved, as you have always obeyed, not as in my presence only, but now much more in my absence, work out your own salvation with fear and trembling; for it is God who works in you both to will and to do for His good pleasure" (Philippians 2:12-13).