That's true, but I always took the atheism of humanist leftists to be the cynical snarky dismissive kind and the atheism of the new atheists, the technocratic atheists to be the hard minded worldly practical kind. I take their alliance to be tentative at best: as between marxists and individualists.

I was a humanist atheist- specifically a Nietzschean, that is a romantic kind of atheist who simply mistrusts the traditional faith on the basis of its standing in opposition to some kind of personal struggle or conception. The social atheists, like Marx and these modern day ID people, distrust religion because it stands in opposition to their more general political project. While the technocrats think that their practical methods are power itself and religion a dangerous opposing pseudo power.

All three of these are only united in opposition to religion, but for vastly different reasons. I for instance, could have given a damn if the clergy opposed communism in Russia or wants certain modifications to the scientific curriculum, but I found it ethical commitments to be stifling and absurd as well as its aesthetics. But the technically minded and the politically minded atheists were inclined to fall into the same issues with me so I could only support them so far. After all, the scientifically minded people always want you to study STEM, stifle any kind of creative impulse inside yourself, and live and die for economic and technical advancement.