In math, there's this thing called proof by contradiction. You state a claim and then follow logically from that claim to get blatant nonsense like 1=0 or a number being both bigger and smaller than some limit. This tells you that your claim is false, because by following it where it leads, you get something that isn't sensible or true.
So it is with hate speech policies. You start out with a claim that 'hate speech is bad and should be banned' and you perfectly logically end up in a place where you censor a major party presidential candidate. That's bad. If you like Trump the person, it's bad. If you can't stand Trump but like his stated policies, that's bad. And if you hate Trump and/or his policies that's bad. Why is it bad? Well, at the very least it makes it impossible to make a fully informed choice in the election.
As a long-time Republican, I posit that if Trump had been under the same kind of microscope last year that he's under today, he'd've never been nominated and we could have a real election instead of this shit show. So yeah: 'bad speech is bad' can lead you to a bad place. Hence, SJW hate speech policiies are bullshit and bad for democracy.