Here's a bit of info on the "incitement to imminent lawless action" exception to the First Amendment: https://en.wikipedia.org/wiki/Imminen...
Here's some footage of the sucker-punching of a protestor by a Trump supporter at a recent Trump rally: https://www.youtube.com/watch?v=WNjoR....
Here's the CNN.com article from which I read Trump's most legally egregious threat: http://www.cnn.com/2016/03/10/politic....
Here's a Mediaite article on that same incident: http://www.mediaite.com/online/trump-....