In general, Milo is invited by Campus Republicans. This is of course within both the group’s and the universities’s charter.
Milo is a political entertainer and provacateur. His views are not outside the mainstream of any right-leaning centrist. He abhors racism and bigotry. But what he abhors most of all is the campus culture which requires free speech to be restricted to “zones”, the ideas of trigger warnings and safe spaces, dislikes identity politics and the notion that special groups need special laws to protect them, and reserves a special ire for feminists who he believes hurt their own cause by taking certain extremist positions.
So, he uses humor and mockery to poke fun at all these things, and does not hold back his opinions in the least.
Hence, protests. Because that’s the way we communicate today on campuses, evidently. It wasn’t that way when I went to school, but apparently things have changed. But it doesn’t look like its for the better.