I have to say that I do think that trump does have the right to speak, but then again others that protest against Trump have that right too.
Still, I do think that Sanders does need to tell his supporters to cool it a notch.
I pointed before that so far it is clear that Trump has been in a bubble, but that was an information bubble to me. But the article does point to another bubble that I should had noticed too, all along he has been making rallies in places where he had lots of support.
Now you tell me that the sooner Trump is starting to make rallies in places were there is more diversity that suddenly he is finding how many do not like him?
As pointed before to you, that will likely make Trump stronger among several republicans, but not all of them. Once the contest goes to the general election the more responsible, moderate and smart Republicans already saw the writing on the wall:
There was a lot of talk before about dismissing early polling, but the early polling did show the general place Trump was going to reach in the primaries. The same pollsters also noted that Clinton and Sanders do beat Trump in the matching polls for the general election, for months already; but more importantly: more recently when people do note now how much likely we will get a Trump vs. Clinton election, the most recent polls are becoming more favorable to Clinton and Trump is losing ground.