I don't know, man. For me, joining the "rationalist" tribe only means trouble, socially speaking. It is not a tight or rewarding community, it lacks solidarity and structure, and we can't seem to agree on suff. However, I would be fooling myself by denying that being inmersed in a European environment that actively enouraged me to not only ignore the edicts of my native religion but to also positively disbelieve in it may have had a role in making a position as a Muslim untenable. However, my change as a rationalist... in the Lesswrong meaning of the term... you could say I had always been a rationalist, ever since I was a small child. The turning point religiously was "Religion's Claims Of Non-Disprovability", which, like many articles here, managed to tie many loose ends that were worrying me for years and made all the puzzle snap together. What Lesswrong did was help me organize my thoughts and show me the natural conclusions of the thought threads that I was intellectually horrified of following on my own. It helped me become more myself, so to speak. So, no, mostly it wasn't a "good social group to join" rationale, though it certainly was a deal-sweetener.