I mean, the rift has always been there and one could even make the case for the 60's and LBJ. there was a lot of hatred between the parties even then. But in today's time, the PC and Identity politics coupled with entitled millennials wanting social justice and we have today's **** show.
One contributing factor is the prevalence of social media, for the simple reason that now everybody can put his or her opinions in writing to share with others in a platform that will reach dozens, hundreds, possibly even thousands. That makes the author believe that he has something worthwhile to say, when in fact the author is simply stating something profoundly and demonstrably stupid.
Once the person believes that what he says is worthwhile, when in fact it is inveterate garbage, the author then feels compelled to defend his idiocy. That leads to a lot of people defending stupid opinions based on pure fiction, and becoming outraged when called out for the idiocy. That fact then undercuts reasoned discussion and debate. The argument is now about personality, and alleged racism and sexism and anti-this or that rather than the facts.
I research my points before I post a comment about voting patterns, or the economy, or the cost of proposed legislation, because it is what I do for a living. If I engaged in fantasy and lies to support my opinion, I would be ripped to shreds in court and lose. I don't, so I am not and don't. Most others don't face that prospect, post garbage among equally ignorant friends and peers, and then cannot accept the fact that they are not only wrong, they are stupidly, embarrassingly wrong.
Ocasio-Cortez is a prime example of my hypothesis. She says things that are comically stupid - "Unemployment is low because everyone has two jobs" [wait, what??], "Illegal aliens are my constituents" [what the ... no, they aren't, since they are not here legally and are not allowed to vote]. "While President Trump's talking collusion, collusion, collusion" [uhh, no, that was actually your party, genius], "Instead of asking, 'Should the Boston Bomber have the right to vote?'” [uhhh, that actually is a pretty good question], "There are parts of Alabama where people are still getting ringworm because they don’t have access to public health" [yeah, going to the doctor does NOT prevent ringworm], "Because we are standing on Native land, and Latino people are descendants of Native people. And we cannot be … criminalized simply for our identity or our status" [uhh, yes, actually, that is exactly how we identify illegals], in insisting that illegals not be held or deported as the law requires, "We are a nation and land of laws, not just [one where] some people are subject to laws and others are not. We are a land of laws" [but didn't you just encourage America to ignore immigration laws??] - but never says, "Wow, sorry, that was stupid" or "Gee, I guess I'm a blithering idiot who should get a clue."
Nope, instead those who point out her idiocy and profound misstatements are racists and sexists. Deal with the content, like I just did? Nope, because racism.