"We all have existential fears; that if you do or permit certain things, bad stuff will happen. If the center doesn't hold, we'll have chaos. If you don't have fears like that, then you don't have a conscience, and nothing personal but I'll lock my doors when you're around.When we don't recognize our own existential fears, then we assume that our viewpoint is identical to objective fact. This is not to say that morality is relative, but simply that the map isn't the territory."
A lot of political tribalism is triggering, or playing off of, existential fear responses. The more sophisticated and malevolent actors in this seek to trigger the existential fear response in their opponents enough to cause a violent backlash while staying just on this side of the law themselves, so that they point at their opponents and claim "they started it!".
Generally this kind of behavior is called bullying, and ought to stop. And while calls for a more civil discourse are certainly warranted, it is not enough. People need to gather their resolve and learn to distinguish between someone who is actually an existential threat and someone who is just trying to trigger you.