Notice how you need to add the qualifier "New" to "Atheist movement" there in order to exclude all the atrocities committed by the old atheists.

Although linking the atrocities of 20th-century Communism to atheism seems to be a favorite trope of contemporary reaction, I'm confused as to why you chose to bring it up in the context of traditional rationality. Marxism might claim an empirical basis, but it's quite hostile to skepticism, and neither its atheism nor its claimed empiricism seem foundational to its social aims. Likewise, Dawkins et al. don't inherit from any of the major philosophers in the socialist family tree that I know of; they're both products of the Enlightenment, but they took quite different paths on their way here.

Moreover, the broader socialist movement isn't at all incompatible with religion: consider liberation theology.