There was the Charles Murray incident at Middlebury, and I'm not in university myself but have a few people on the academic track on FB. On a few occasions I've seen them circulate petitions to no-platform people that were going to attend their universities.
I didn't follow if they succeeded or not, but it is to me a questionable attitude for someone who calls themselves an academic.
Of course in the world people will hold minority opinions of all kinds and we have better uses of our time than fretting over those, or exaggerating their relevance. But this wasn't so much a part of university culture just a decade ago when I was there.
And one issue is that this isn't usually the university department putting on a conference and coming to the conclusion that Milo would be a worthy speaker. More a student body (usually conservative) that chooses to invite someone. Its also not fair to allow a student body to exist, and then start vetoing their guest speakers. The most adequate response in my opinion is to just to ignore the whole thing, like I did when new keynesian economists were speaking
(I know, I'm repetitive... and I'm suggesting what most students already do).