Sorry - you are nitpicking. If there's a "silly smokescreen", it's the sort of procedure you are following. Actually, I don't want to call you "silly", because I don't want to adopt the contemptuous attitude towards Atheists which many Atheists have towards those who don't agree with them.
Incidentally Nazism, whatever its roots, was basically not "Catholic" but atheistic, elevating the "Aryan race" to the position which a god might have held. As for "Personality Cults" - they occur among all groups, but it could be argued that an atheistic background makes one easier to set up - less opposition to the idolisation of such as Stalin, Mao, Kim il-Sung etc.
Many people have been persecuted, tortured, and killed in Atheistic countries (Soviet Union, China, Eastern Europe) because they have opposed the Atheistic policies of their governments. Ever read of what has happened to Buddhist monks in Tibet? If those aren't terrible things done in the name of Atheism, then I suppose "Atheism" has been so defined in a way that it would be impossible to blame it for anything. End of intelligent discussion.
I think it is pointless to indulge in this "who is responsible for more atrocities" sort of thing. As I pointed out, all major ideologies have their evil, and their good, sides. The sort of "point-scoring" on atrocities seems to be mainly indulged in by the arrogant and intolerant, on all sides.
There are Christians, Moslems, Atheists, Sikhs, etc.etc. who are filled with contempt for all those who don't agree with them, and are constantly trying to denigrate the others as uneducated, silly, stupid, evil etc. - Atheism is certainly not free from this tendency. There are also those in all these groups who are more concerned to bring about understanding, tolerance, and respect for those whose views they don't agree with.
I know which of these alternatives I would rather be my goal, though being a fallible human being, I don't always manage to live up to it.