I've been going to protests in DC since 1969.
I've seen mounted park police ride right over demonstrators
I've seen one club a non-protesting passerby for absolutely no reason during May Day 1971.
I've run through clouds of teargas sprayed by the cops.
I've seen them arrest groups of people for no reason.
The last big Iraq war protest my husband and I attended, a group of us, mostly peaceful older folks like me, were walking up a street that the police had directed us to use, when we were suddenly stopped and herded onto a side street and surrounded by DC cops on motorcycles in riot gear. Nobody was allowed to leave that one block area, even people who had absolutely nothing to do with the protest. Nobody was allowed to sit down, and there were elderly people who desperately needed to get to a restroom. The cops were joined by riot cops on foot, and it looked like we were all going to get beaten and arrested. And from the looks on their faces, many of the cops were looking forward to it. Beating up about 70 people who were mostly in their 50s through 70s. No reason was ever given for why they detained us.
After more than an hour of quietly standing there, scared shitless, we were saved by some journalist who spotted us and started asking questions about why we were detained. At one point Chief Ramsey showed up and was also questioned by the reporter. About 20 minutes later, we were permitted to disperse.
The DC and National Capital Park police, in my opinion, contain in their ranks a bunch of crazies who love nothing better than beating the crap out of us "commie pinko hippies," African Americans, etc. And I write this as a former newspaper reporter who associated a great deal with police in NJ and even had a couple of friends among them.