All you have to do is watch some of those 'Man on the street' videos various people do, like Nick Shirley or James Kurg, to name a couple. When they go to some Leftist protest, or just somewhere you find a lot of people with Leftist views, no matter how polite, how reasonable, how neutral their questions and actions are, the Leftists immediately label them extremists and start trying as hard as they can to shut them down. The Leftists usually won't engage in a conversation, or if they do once they realize they are being backed into a corner with their views, they turn hostile.
It's no different with Leftist run boards. Question the orthodox views, don't parrot the party line, and you get banned in a nanosecond.