That said, the key to a free society is peaceful exchange of ideas. Don't like his ideas? Great! Critique them! But the fundamental human rights guaranteed under the Bill of Rights include the right to assemble and speak freely. I would note that rallies to listen to the ideas of a presidential candidate are precisely the situations those who drafted the Bill and those who ratified it envisioned.
Let's leave the thugs out of the picture. If you want to protest, fine. Be peaceful and do impede the exchange of ideas from those who came to hear what the candidate said. You do not have to agree with anything you hear.