I believe it is well-known that the issue with the right is they see "American Culture" as something predetermined and immutable. Whereas, in reality, "American Culture" itself is a product of constant social change and disruptive innovation (e.g., the United States' founding was a direct consequence of the rebellion and sedition against King George III).

The issue with the left, on the other hand, is that they overlook the tremendous time and effort it takes for most change to occur to achieve the social condition they prefer—provided that such a social condition can be maintained over time (i.e., it becomes part of future's "American Culture"), a precondition they often fail to take into account.

But the toxicity we see today appears to go beyond the traditional left-right dichotomy, and there could be many complex reasons behind it. One possible factor I can think of is information overload resulting from technological advances, which has dramatically exaggerated people's expectations as well as fears.