I'm friends with a couple of people on Facebook who post way too much. One posts a huge amount of strongly political stuff (most of which I happen to agree with anyway so it doesn't matter so much). The other posts way too many pictures I've seen before of kittens and so on. I didn't want to completely cut myself off from them by hiding all their posts so what I did was, I unsubscribed from them, then I created a friends list for each of them which they were the only person on. So if I ever want to see what they've been posting I just click the list on the left-hand menu and scan their posts quickly.

what sort of society do we promote when a social media site becomes the primary means of discourse? What does it say about us and our values?

It's not the primary means of discourse, people still see each other in real life. If they stopped doing that I might start getting worried, but I don't think they will. Calm down.

There's a skill you should learn, which is how to ignore people, how to stop caring that their views are stupid and wrong. It's a very useful skill to have these days. I admit it's not an easy skill to acquire, but it's a worthwhile one.