Good point about Christianity, but no, atheism isn't absurd, although that could be just a semantic question about labels. If you attach the word "God" to Being itself, or to the ground of spacetime, but you don't assume that that Being is personal or that it performs miracles, created nature, and will reward its followers in the afterlife, then that notion of "God" is consistent with atheism in the standard, modern sense.

I'd say Peterson muddies the waters also by being a conservative with an authoritarian personality. That makes him arrogant when he's a dilettante. He thinks he knows more than he does. Also, he's sold out to appeal to the alt-right crowd, so he has an economic incentive to save face and disguise his ignorance. He's a demagogue.