But why would you feel the need to tell someone their opinions are "silly" when they're NOT proposing state-sponsored control over others' lives based on their own belief systems?

Earlier, you said: "...all religions have their Orthodox, hollier-than-thou idiots that push their sh*t on you."

I would agree with you, when it comes to that statement. But I'd also add that such a know-it-all mentality can also extend to SOME people who subscribe to atheism (usually the more gnostic forms of it).