I agree there's a lot of shitty judgey ppl out there, in all different forms of life.
As an atheist, I have met the smug atheists you pointed out. From my perspective, I liken it to the kids that found out Santa Claus isn't real. "Can you believe, Jerry still believes in Santa" At the same time knowing before they saw mommy shoving presents under the tree, xmas seemed simpler, more enjoyable. Eventually they come to terms with it, realize what xmas is supposed to be about and the smugness dissipates. - I realize this analogy can be perceived as smug, but just putting it in the perspective of a non-believer.
I personally don't care what you believe as long as it makes you feel grounded with a purpose and you don't wrong others.
I'm not inclined to believe that being pious makes you a better person than someone who isn't or vice versa.
And then there are the ones that just believe they are smarter than you and complete d-bags. We all have them.
I would be remiss however, if I didn't mention the eye rolling I do when an athlete/actor/musician, etc... thanks God for their victory/oscar/grammy.