In the wider world, even things like atheism are "extremely controversial," but I don't think we need to make dramatic shows of uncertainty and humility every time someone brings it up; most all of us here are atheists and we need to move on and discuss the more difficult questions.

I don't think the primary reason to not discuss atheism and theism at LW is because most readers of LW are atheists. What that implies to me is "if we all believe X, X is not worth discussing; if we are conflicted about Y, then Y is worth discussing."

What I would say instead is "Z is worth discussing to the extent that discussing Z is productive." There are topics where it would be great if we all agreed, but discussing those topics predictably does not lead to more agreement. That is, I would view it not as we are interested in more difficult questions, but in easier discussions.

The easier discussions are often on more sophisticated topics. For example, it's often easier to have an abstract discussion on what it means to believe something, and what it means to change your mind, than a concrete discussion on Lewis's trilemma.