Would we need to do that? Why would we consider those things "atheism"?
I mean,
1) AFAICT, none of them even require atheism.
2) It seems absurd and chauvinistic to me to frame things done by people who aren't theists as "consequences of atheism."
On the second point: would you say that the water pollution associated with golf courses, for instance, is a consequence of not playing baseball? How about bear attacks in national parks while people are camping? Both of these things are "consequences" of not playing baseball in the sense that if someone played baseball instead of engaging in those hobbies, the impact of those other hobbies wouldn't have happened.
Framing things done by atheists as "consequences of atheism" suggests a bizarre and IMO unjustified focus on theism - or the lack thereof - as the defining characteristic of a person or a belief system.
I specifically chose ideologies in which atheism is a core facet of them, in the same way that theism is a core facet of, for instance, Christian ethics.
Existentialism, Secular Humanism, and Social Darwinism were all philosophies formed in response to the loss of religion and the need for a new ethical system to replace it. They derive from atheism.
Stalinism, likewise, views religion (and theism) as a political obstacle and a lie that prevents people from recognizing the reality of their situation and staging a revolution. Similar to the above philosophies, it sees a necessity to replace religious devotion to God with a nationalistic devotion to the state, almost directly because there is no God to depend on and religion is an "opium of the people."
Machiavellianism is meant to be an atheistic description of secular power dynamics. It's essentially advice given from a position of atheism and from the perspective that all morality, which at the time was almost exclusively associated with organized religions, was an illusion. It can't wholly exist without atheism, because its entire position is based on a rejection of any sort of governing supernatural force of law.
So in all of these above examples, these philosophies are direct consequences of atheism in the same way religions can be direct consequences of theism. The only argument you're giving here to counter that seems to be some form of special pleading.
LaVeyan Satanism and Buddhism might be the only ones where your counter-argument holds that they're merely atheistic philosophies and not philosophies formed as a consequence of atheism. Except, historically, both historically differentiate themselves from their predecessors by the fact of their atheism and the consequences that atheism has on the religion. For LaVeyan Satanism, that's Thelema, and for Buddhism it's Hinduism. So while the case is looser, I still think it's a fair comparison.
So if we're going to consider Muslim terrorism a consequence of theism, we also have to consider the USSR a consequence of atheism.
I don't think we should consider Muslim terrorism a consequence of theism or the USSR a consequence of atheism. I think we should view them as consequences of particular individuals ascribing to a specific interpretation of certain philosophies, thus avoiding over-generalization. But if you want to make the comparison, then do it consistently and coherently. Don't special plead.