Some do organize into groups. I find this spurious since casting off religion means rejecting a form of unnecessary collectivism only to embrace another; it seems partially counterproductive.
But most non-believers don't organize, and chances are that you know many atheists who just don't discuss their beliefs in day to day conversation.
Atheism is just a religion of the Godless, obsessed with attacking other religions in the belief that they are the superior thinkers.
This is a fundamental misunderstanding that you have about atheism, non theism, and non-belivers.
You don't espouse the beliefs of Thor, Apollo, Ahura Mazda, or many of the other gods of the world. There's no dogma, faith, arrogance, or 'religion' required for you to not believe in them. Perhaps you've studied their scripture, text, and history and come to the conclusion that they're not believable or rational. Or maybe you just think they're ridiculous at face value.
Now, simply imagine someone doing the exact same thing for the scriptures and tenets of the major Abrahamic religions, and who came to the same conclusion.
It's not irrational or the least bit 'religious' if you give it an honest look.
Not all atheists believe in nothing. Many believe in govt and socialism and worship it like a God. Technically they’re atheists, but not in the sense of the normal use of the word.
Those are the ones who scare me, not the garden variety non-believers in God.
Actually, those others you mentioned such as Thor etc., have their explanations in the believe also in evil. False Gods, created by Satan. So while I have no faith in them, I believe their concept exists in that there is another spiritual force behind them. One great evil with many masks. Thor exists, like that wolf in sheep’s clothing. As do the others.
I believe that those who say there is no God have been just as fooled by that same spiritual force.