One more observation about Trump's violent rallies. They serve a real, practical purpose for the nomination phase. Trump needs the Republican Party to be afraid to take the nomination away from him. The threats of a third party run serve that purpose, but right now, the brokered convention strategy is particularly susceptible to this kind of threat.
As I have written before, Trump is highly likely to get a majority of delegates. However, if Cruz and the rest can hold Trump below 50% in the delegate count, there is at least the potential for someone else to get the nomination. The problem, as I have written, is that taking the Democratic nomination away from McCarthy in 1968 sparked riots.
And those were hippies. Trump's supporters aren't exactly hippies. What do you think they will do if a backroom deal takes the nomination away from Trump at this point? The repeated, violent incidents at Trump's rallies serve to remind the party establishment of what will happen if they try the brokered convention approach to defeating Trump. There will be widespread riots. If the party wants to avoid that, then even if the delegate count puts Trump below 50%, he will still get the nomination.