Not all political activism is democratic. For example, just a bit ago some very politically active people decided to violently attack the US Capitol in an attempt to obstruct the culmination of the democratic process. That's not an expression of democratic values.
Yeah, political engagement was likely near its peak during the Civil War. I don't think it's as positive an aspect of polarization as the OP suggested.
this is an interesting conundrum, similar to the paradox of tolerance. In the end, we will likely draw a line based on an arbitrary rule, like any authoritarian would
