Cruz did NOT blame Donald Trump.
Trump certainly has the right to have his rally unencumbered. Equally, the protesters have every right to show up and protest just about as loudly and obnoxiously as they like — as long as it’s peaceful and they don’t try to disrupt.
Now, I will say that I think Trump selected a place for the event that was probably unwise. Another location might have reduced this problem. Having it on the college campus made it way too easy for the protesters to do what they do.
A lot of violence seems to follow Trump. He has personally threatened demonstrators and asked his supporters to punch them out. His campaign manager attacked a reporter simply for asking a question. His supporters have violently attacked minority protesters. But somehow, that has nothing to do with him.
So you can say that something about his campaign is fostering such an environment.