Your list has little or nothing to do with atheists killing people simply for being theists. The killers you list were not all atheists - certainly not by the standards of the OP of this thread - and as far as one can tell their victims were not selected for their theistic beliefs.
If there is an example buried in that list of some atheists selecting and killing theists simply for being theists, as required, perhaps you might do us the courtesy of pointing to it?
They didn't, mostly. Certainly not in, say, Uganda. And if they had, they would have been looking at registries indicating political allegiance (tribe, church, language, Party, etc) - civic registries of theists don't seem to have been all that common.