So, the reason that people I know are so horrified by Milo is that he was calling out undocumented and transgendered students by name; not just talking about what he dislikes about these groups, but calling them before the mob of his audience on an individual basis, knowing full well that many of his audience members would go find that person and take out their issues on that person, all while not even trying to hedge the situation to demonized his own followers who turned to such levels; and, for the undocumented, essentially turning a microscope on them and making it highly likely they could find themselves deported.
This, to me, fits a usage of the term "violence". Maybe you disagree. Maybe the author also disagrees, but I don't know, as I will now again say that as the author didn't even ask this question, which let them respond to a weird philosophy piece that also didn't seem to care to ask anyone involved, which I find so ludicrously questionable in their position and with their clear understanding of other issues as to be outright dishonest. This is an article talking with another article about a group of people, and yet those people were not consulted? This should not happen.
Regardless, with this information, you now get to do what the author should have done: discuss whether you think this speech is violent--not just any speech, and not the perfect speech that this author might hope you are expecting, but the specific speech involved in the incidents on college campuses which are used in the author's examples and that are required to claim the reactions are incompatible. In all seriousness: even if you still disagree that Milo is violent, I hope we can at least agree that this article sucks.