Thank you for disagreeing with statements I actually made. Apologies in advance for the length of this reply, I don’t have time to make it shorter 
The point I was trying to make is that extremist groups leverage rejection and other negative social interactions to promote group solidarity, drive recruiting, and further radicalize existing membership. Their leaders use their enemies and detractors to perform a task for them. It’s efficient.
You pointed out that most people are polite, and I’ll concede you’re right. It used to be necessary for the cults and hate groups to send their members out door to door for days at a time in order to experience the vilification that the leadership uses to condition soldiers. Nowadays, they just have their recruits do duty on imgur or some other ostensibly liberal site, which is a faster and easier way to get the desired juices flowing.
This dynamic is why SPLC and other highly effective organizations advise countering hate with love and unity rather than confrontation. But of course, they are talking about physical meatspace events - it was me and not SPLC making the claim that virtual spaces can be used the same way.
Political and social movements rely on community. Everything you said about human socialization is, in my opinion, entirely correct. I can bring people into my community, and they will come to share my goals and values if I play my cards right. Or I can revile people who don’t embody my ideals and properly pronounce my shibboleths, driving them out, and they will probably join some other community opposed to mine.
The modern GOP is trying to gather every disaffected group they can; they are desperate, they will pander to anyone (the Log Cabin Republicans are still a thing, right?). Trying to recruit people who are offended that they can’t blow smoke in your face is totally on brand for them. They are offering those people a community.
