In Louisville, police have investigated an incident where a Rand Paul volunteer reportedly stepped on the head of a MoveOn activist, though as I write this, nobody's been charged. Rand Paul's campaign was NOT amused; they've banned the gentleman from future events, and he's lost his spot as a campaign coordinator.
For his part, he has apologized. He says the video of the incident makes it look worse than it was. (There was stepping, though it looks more like the shoulder /neck area. I'm not an expert.) And he argues that police should have gotten involved earlier -- the MoveOn activist was trying to give Paul a fake award.
Hat Tip: Many thanks, aqua, Keith G and Anonymooses!