I’ve ran across a few in real life as well. The main thing they have in common seems to be religious recoil. They used to be religious, but realised that it was false. Unfortunately, losing the nostic part is harder than losing the theistic part. They tend to over shoot, and become quite radical.

On the plus side, they tend to settle down. It takes time (sometimes years) to find their new equilibrium. I wasn’t particularly religious growing up, but even I had a bit of that recoil effect for a while. I’ll still go toe to toe with a religion enthusiast, if required, but try not to instigate the “discussion”. I just step in when their public views need balancing out.