If attendance is optional how is it boycotting if they decide not to come? However boycotting extends to censorship when this is extended to try and stop others attending such events, cause destruction even attack people or turn up and shout down the speaker. Some take a pride in this.
Universities are supposed to be halls of knowledge and debate.
I picked some Youtubes on Milo but cannot see any reason to simply ban him. He can't be homophobic since he's gay, and likes black men.
Yiannopoulos claims he used to walk around with a color strip they use in paint stores so he could hold it up against a guy's skin to see if he was dark enough for him to fuck. He self identifies as a sociopath and is probably the most well known misogynist troll on the internet. He instigated and led the harassment, bullying, and threats to Brianna Wu and Anita Sarkesian, as well as the recent over-the-top harassment of Leslie Jones.
He's a Grade A asshole who thinks being a sociopath makes him cooler than everyone else.
I don't believe he should be silenced. I also don't believe he should be admired or encouraged. I certainly don't think he should be coddled. And I don't believe the 1,500 people having a peaceful protest against his hateful spew should be blamed for what the hundred or so violent, mask-wearing thugs did when they arrived an masse to stir shit up.