"There is a website I can't link that is taking money to crowdfund doxxing efforts. After the admins banned that domain, the mods on /r/altright continued to manually approve submissions to that site and added them as sticky/announcement posts. My guess is that is the reasoning behind the ban."
So they got banned for repeatedly and intentionally, with moderator support, circumventing Reddit's rules -- not for 'suppression of free speech' or anything like that. I'm sure the admins were glad to be rid of them, but, they really brought it on themselves.