Often when Christians bring up morality, they try to dump Stalin, Mao and Pol Pot on Atheism to score points.

The response from Atheists are varied but they never seem to call the Christians on their categorical fallacy.

When you say they are Atheists that is true, but it is also true to say the Crusaders were Theists. This does not mean that the Crusaders were Muslim, Hindu, Jewish or so on.

Meanwhile the accusation is that all Atheists(Raëlians, Buddhists, Skeptics and so on) had the same beliefs as Stalin, Pol Pot and Mao.

Theism and Atheism address a question. You cannot accuse all Theists for the actions of Catholics nor can you accuse all Atheists for the actions of Maoists.

Or am I wrong?

Apologies for any punctuation, grammar, coherency and spelling issues. I am a poor student of written English.

I think there are two issues here. First, is that beliefs inform action. Since atheism is the lack of particular class of beliefs, it's difficult-to-impossible to justify the claim that Stalin, Mao, or Pol Pot committed genocide because they lacked beliefs. In all cases, they acted based on what they did believe, which had nothing to do with atheism.

I agree with you that it's wrong to lump ALL theists together, but Judaism, Christianity, Islam (and all splinter religions) believe in the same God (the god of Abraham, thus they are called the Abrahamic religions.) Furthermore, members of these religions claim that this God is the author of morality, that they can receive messages from the god, and that they are generally very motivated to serve this god (so they can gain the god's blessing and/or achieve perpetual orgasm). Given this set of beliefs, it is reasonable to expect that members of these religions should generally be well-behaved and have a consistent moral code. Of course, any way you look at it, the idea fails. The main failure seems to be that the three religions nor their various sects cannot agree on anything of substance. They've killed each-other over their religious differences ever since the beginning.

Atheists, by contrast, have no claim for a centralized moral authority--we only have our common evolutionary history, ability to empathize and reason, and our common culture, including laws. Strangely, despite our apparent lack of central authority, we've done much better than those who clam to have one.

My problem is that the premise of their argument is flawed and rarely if ever are they called on it.

Atheist and Theist are two categories and the sub-categories are the various religions such as Christianity.

Often Christians will assert moral superiority by comparing, all the Good Christianity has done and all the Bad Atheists have done.

Is that not the same as saying, "Fruits are Good for you, look at all Inorganic things that are Bad."

It bother me because that is part of the reason Atheists reject the God of the Bible. While a God may exist, the God of the Bible is a flawed premise that we can discount based on the contradictions.

Perhaps you can rephrase or simplify that and feel free to do so.

Thank you for responding, I agree with everything you've said. Although I have noticed some people claim Atheists are Morally Superior.

My point would be that Atheists are not Morally Superior because we don't believe in God. As do most people in Modern Societies, Atheists tend to reject Bronze Age Doctrines of Morality.