I definitely believe the guy was in the wrong here, but what would have happened if it were a leftist harassing Trump supporters?
when the candidate you choose to support openly wants to make life harder, more difficult or even non-existent for groups of people you've chosen your side and be prepared to defend it.
edit: went to the other thread minimaxir linked to, read some of the examples. The guy was behaving like a total asshole. Some purely left-wing analog of the same behavior wouldn't last long anywhere.