If all he'd done was criticize a movie or a celebrity, nothing would have happened but what what he actually did was to repeat racist slurs[1] and incite other people to attack her by reposting fake screenshots as if they're real[2], and continuing long after it was clear that she wasn't interested in hearing from him or the rest of the GamerGate brigades.
> Harassment: You may not incite or engage in the targeted abuse or harassment of others.
> Hateful conduct: You may not promote violence against or directly attack or threaten other people on the basis of race, ethnicity, national origin, sexual orientation, gender, gender identity, religious affiliation, age, disability, or disease.
Not to defend Milo here (it certainly sounds like he deserved to be banned for harassment), but the tweet in this screenshot doesn't seem to be him? It's from "evyarb9000", and from a quick Google search, Milo's username was "Nero". (He must have grabbed that handle pretty early on...)
As a private company, Twitter is under no obligation to provide anyone with a forum and their terms of service (https://twitter.com/tos and https://support.twitter.com/articles/18311) very clearly exclude that kind of behaviour:
> Harassment: You may not incite or engage in the targeted abuse or harassment of others. > Hateful conduct: You may not promote violence against or directly attack or threaten other people on the basis of race, ethnicity, national origin, sexual orientation, gender, gender identity, religious affiliation, age, disability, or disease.
1. Called her an ape, echoing a long history of racist comparisons: https://twitter.com/Lesdoggg/status/755182965060169728 2. Examples at http://www.vox.com/2016/7/20/12226070/milo-yiannopoulus-twit...