Certainly, the whole idea is that theistic belief is separate from morality after all.

And yet examples are remarkable. The one you met wouldn’t have been memorable otherwise. At a guess, it’s rare because atheism is the kind of hair-shirt or “kick me” sign that actual assholes rarely choose, as it tends to require a fair amount of introspection.

But I have known a handful of assholes who go around telling everyone they’re an asshole, as if the negative attention is the point. Usually I associate that behavior with baggage related to abandonment and rejection.

In that case, conservatism and other socially maladaptive ideologies might be secondary to unresolved trauma, shame, fear, and self-hate. And for that, therapy is the only solution I know, not religion.