@SD,
" Private individuals can restrict it in their areas as they see fit. Including the college, including the company hosting the speech, et cetera."
Well, first of all, it was a public university, so no, they can't. (Public universities can restrict quite a few types of student speech, actually, but not at political events).
I also doubt there was a "company hosting the speech" that would be more controlling than the public university campus. And finally, there remains the fact that it was *probably* secret service. The "company hosting the speech," if it was they, would just give their reason, not cite "security concerns."
There's a further fact, of course, that even if it was not an *illegal* restriction of free speech (we don't really have enough facts to adjudicate that for sure, though there is a decent chance it was), it was still a restriction of free speech that should not have happened in our polity.