I don't usually participate in communities of my interest, like vegan, communist, anarchist, etc. because I know I don't agree a 100% and that there will always be people that think are better than others or that have a lot more time to spend on activism than me. But all my friends know I never back down when discussing important topics with anyone, I always tell them that I will take the time to discuss with people they don't like, like weird conservatives and other uncomfortable groups (which have a big presence where I study).

I usually can recognize when someone is close to being more left-leaning than what they think they are, and I take the time to talk to them about it, which a lot of leftist communities don't (at least from what I've seen). Yes, there are trolls, but usually when talking in person, they aren't that stupid.