Being confrontational doesn't mean being violent. Non-violent ways to be confrontational can include refusing to disperse, not staying within the previously agreed spaces (if any), occupying public space, harassing the police, etc. And the sheer mass of protesters can be already intimidating and cause a police reaction if things are not extremely well managed.

Btw, I was looking for large right-wing rallies in the US, and couldn't find any. The "unite the right" rally seems to have gathered a few hundred people in all. Compare with the largest BLM rally in Washington DC, 200 thousand people. How do you compare these two (even if the participants to the first are nazi-like nutters and those of the other are normal left-wing citizens)?

And the "unite the right" are the nutters. Where are the large (tens of thousands of participants) rallies of the moderate right? Like the "keep taxes low" rally and the "no medicare" rally?