It has nothing to do with superiority of atheism or theism. It's irrelevant. The point is when you make your argument based solely around religious belief, you will never convince anybody to believe your position through that reason without converting them to your faith. At which point, you're proselytizing your faith, not discussing the topic.
It's why faith-based arguments are inherently weak. If your whole argument is "X is wrong because God says so", then anybody who doesn't believe in your god will never be convinced by that argument. They may agree with your opinion, but your reasoning will never be pointed to as the reason for agreeing with it unless they share the same faith.
This is why moderation is necessary. If you can't recognize the difference between no arguments, weak arguments, and strong arguments, and all of them are allowed, then it defeats the purpose of a discussion forum. Particularly opinions with no arguments in them. If these types of posts are allowed, then it might as well be an opinion forum. Discussion is built around the exchange of reasoning, not the exchange of opinion. If you can't figure out how to justify your opinion, then this honestly shouldn't be the place you're posting. Everybody has an opinion. What makes an opinion valuable is when you can defend it from contrary opinions.