Why has public discourse become such an exercise in polarized futility? There are many causes, no doubt. Here are some that I am pretty sure are significant contributors.
I frequently encounter people who do not seem to understand the difference between a fact and an assertion. To them, a “fact” is simply an assertion with which they agree. A “false fact” is an assertion with which they disagree. And “evidence” or “argument” mean repeating the assertion more loudly, more passionately, and/or with fancier rhetoric. These people appear on both sides of the political divide. Mindlessness in Public Discourse
This kind of inability to participate in valid forensic reasoning has always been with us, of course. But I think at least two current influences are making it worse.