Look I don't want to go too far with this analogy. It's flawed and there really are many variables, but you know, as someone who teaches the morphing of Weimar Germany into the Third Reich, the whole violence at political rallies thing obviously raises a few disconsonant tremors.
The Trump rally in Chicago had to be cancelled because protestors violently disrupted it. Not Trump's fault you might say. And you'd be wrong. A couple of days earlier, at another Trump rally in North Carolina, one of his supporters socked a protestor firmly in the face. And wasn't it Trump who calmly noted that "I'd like to punch them in the face, I really would" when referring to protestors who dared disrupt his meetings?
It's no great surprise that if you deal in the politics of populist hate and demonise whole sections of the population, then you might get throw-back in your political meetings. Hate isn't easily contained. And what starts in a campaign can easily go on to infect a whole nation. Political leaders have a responsibility for the way in which a nation's discourse is conducted, and it's one which Trump is failing mightily.