Originally Posted by kane

Actually, on that point, yesterday's protests started off with a sit in on a bridge that blocked traffic on it. The police were calm and cool and arrested those who were sitting in and there were no issues.

I think the differences here is that the crowd was pushing on them and were getting pretty riled up. Check out the video I have linked above and you can see people pushing back. To me it is different from just sitting and being peaceful. Just the night before there were some incidents where those in the crowd injured a few cops by throwing bottles at at them.