Why shouldn't atheists criticize or scrutinize each other's thinking?
Why do you think they don't? Now, I may be a bit behind the curve in this particular discussion, because most of it is just tl;dr rambling that reeks of having just been pulled out of the speaker's ass, but why wouldn't atheists argue and bicker amongst themselves? Or do
you just mean "why don't they sit around saying 'why don't you believe in God? What, that's not a very good reason, you should be a christian instead like all good people are' to each other"?
Now, to be more serious,
I believe your point was something along the lines of I see, from what you posted while I was typing this, that it's apparently not this, as I assumed, but rather the point bolded above, which I originally included as a joke thinking it too ridiculous to be true, the rest of the post is left as my contribution to the discussion, as I was planning on writing it anyways "why don't they stop each other from thumbing their noses at religious folk?", or why they themselves may do it
, correct?. Both are rather obvious, when you think about it. For the first, because, in any combination, a) they don't give a shit, b) they don't know the people, c) can't do shit about it if they wanted to, or d) agree with it but don't care enough/have enough time/energy to do it themselves. For the second, a few more obvious factors are at work, all stemming from the fact that they're human.
First off, as far as their proselytization goes, how they rationalize it is rather irrelevant: it's the same damn reason any of you are bothering to argue your point on the matter, or any matter really; same reason people socialize in fairly ideologically homogeneous groups. Humans are driven to attempt to socially homogenize their environment: someone who acts different from the group must be shown the "error" of their ways, or driven off. Tribal instinct at work; it doesn't need rational justification, it's just programmed into your head. It makes sense in a tribal setting, less so in the context of modern superpopulations and ubiquitous connectivity. But we've mostly been living in some form of tribal life up until a few hundred years ago, and a fair number still are (counting rural villages as tribal enough to fit this concept). Millennia of selection won't be undone by a few
decades of hippies spewing "tolerate everything and know that everyone is a special little flower who should be totally different and shit man". And atheists, by the way, aren't hippies, and they don't all subscribe to that silliness.
Second, as to why some seem to get off to thumbing their nose at the religious: again, tribal instinct. They're driven to lay down lines in the sand, so to speak; define themselves as a social entity that's not afraid to stand up to the monolithic incumbent culture. Now, they would be afraid if there weren't laws and watchdogs stopping the incumbents from just going off and lynching them,
like they used to get away with.
Also on that bit, many atheists do *hate* devoutly religious people, at least ones they don't personally know. It's all just an amorphous blob of "people whose beliefs are diametrically opposed to my own". The exact same goes for the devoutly religious, though on both sides most are too polite or have too much sense to voice their feelings out loud, at least in public. Trolling them, one way or another, is just a way to feel you've inflicted some harm on your "enemies", in the form of causing them some stress or wasting their time arguing with you.
Now, Idiom, you're either trolling, or just have no clue what you're talking about. You're saying atheists should either organize into formal, christian-esque splinter factions, or just stand as one man social groups? Not a whole lot of ways someone can take that.