I'm of course not literally calling it "my" platform. I'm pointing out that the student body and faculty of the university (or the TV show host, or the convention organizer or what have you), they are the owners of the respective platforms. And they get to choose who to allow and who not to allow to attach themselves with their brand name.

In case there are any illusions, the hate-mongering trolls are not there to engage in intellectually vigorous debate. They are there to buy themselves a patina of respectability by attaching themselves to these respectable brand names. These institutions would be fools to allow themselves to be used that way.