Does your logic still apply when the police are doing the violent acts to try to get the protesters out of the building? Is it the candidate's fault that a bunch of leftists who were involved with the protests in Ferguson decide to cause trouble?
It is the protesters fault. The End.
The candidate is responsible to not create an environment where when these thugs show up, the supporters want to beat the crap out of them based on previous statements by the candidate.
I have been involved in many pro life demonstrations where I have had to keep my cool under much duress.