Trump's own words, from some of his rallies. He seems to enjoy a good ol' punch up, especially when it's his "passionate" supporters delivering it.
"if you see somebody getting ready to throw a tomato, knock the crap out of 'em, would you? Seriously. Okay? Just knock the hell — I promise you, I will pay for the legal fees. I promise. I promise."
"Get him out. Try not to hurt him. If you do I’ll defend you in court." "Are Trump rallies the most fun?" he then asked the crowd. "We’re having a good time."
He then recalled an incident at a New Hampshire rally where a protester started "swinging and punching." Trump said some people in the audience "took him out."
"It was really amazing to watch," he said.
"See, in the good old days this didn’t use to happen, because they used to treat them very rough. We’ve become very weak."
In November, a Trump supporter "punched and attempted to choke" a protester at a rally in Birmingham, Alabama (according to the Washington Post); Trump said afterward that "maybe he deserved to get roughed up."
http://www.vox.com/2016/3/11/11202540/trump-violent