Been like this a good long while by my reckoning. Social media just exasperated it and puts it into the public eye more. You'll get the crazy voices magnified a millionfold where they were practically invisible before.

Most people are reasonable and not completely so far gone but they are susceptible to propoganda as we all are. But it only takes a few emotionally unhinged and crazy people in a group to poison the dynamic. Mostly how it works now is the crazy fringe takes get picked up by the opposite side to use as propoganda to show their base how bad the other side is even though it's a minority fringe take, and that tends to give that take more ground as you get the counter reaction of "the bad guys are attacking this guy for saying this, but actually they have a point" and spin it back to get their base into accepting ideas that may not have been popular before.

You'll get crucified online now if you mention that both parties are essentially engaging in similar propoganda techniques to eque out thin winnable margins in elections, something about "same thing both sides" fallacy or what not as they'll say they are the good side and the other side is the evil side. Of course both sides actually do tend to say this so it's pretty funny to watch when two people tend to agree on the problems with American society from a very general perspective only to watch them come to realize in horror that they are on opposite sides of the fence and therefore they've been talking with one of the evil ones.

I'll fully concede that positions on policy do matter and aren't identical but there's so much finger pointing and downright insane histeria going on now that it's basically impossible to have a discussion about anything in an open forum without it quickly devolving into an insult match. The tragedy of the commons I suppose. Only takes a few people pissing in the pool to make everyone else leave.