I'm not going to address the broad subject of Twitter banning the needy, cynical huckster Milo Yiannopoulos. It's been done, you know what I'd say, and I don't have much to add.
I'll address just one small piece of the story. Before he was banned, Yiannopoulos retweeted bigoted tweets fabricated to look like Leslie Jones had uttered them. The tweets were fake, and Yiannopoulos knew they were fake.
Was it defamatory for Yiannopoulos to circulate the faked tweets falsely attributing bigoted statements to Jones?
The answer: probably not, given Yiannopoulos' reputation.
Only false statements of fact can be defamatory. Satire, ridicule, and insults cannot. The faked tweets were intended as trolling and — to use the term extraordinarily generously — "satire", not as a factual claim that Jones had uttered the words. Could some people look at the fake tweets and assume they were real and that Jones actually said those things? Yes. But courts give very broad protection to satire, and protect it even when some people take it seriously. In determining whether a challenged statement should be taken as satire/ridicule/insult/hyperbole or as a statement of fact, courts look at how a reasonable audience familiar with the speaker and the context would take it. In other words, the relevant question is whether the speaker's target audience, informed about the circumstances surrounding the statement, would take the statement as an assertion of fact. I wrote about this in 2013 when I described a D.C. Circuit opinion rejecting a WorldNetDaily lawsuit against Esquire. Esquire's satire of Joseph Farah and Jerome Corsi was protected people readers familiar with Esquire would recognize their story as a parody, not as a news story. Similarly, readers familiar with Popehat would recognize that my accusing Farah and Corsi of sexual molestation of walruses was satire serving as an example of the doctrine, even if someone unfamiliar with Popehat or the case might take it seriously.
Here, a reasonable audience familiar with the context (Yiannopoulos trolling and attacking someone for clicks and attention, and playing to his hooting bigoted admirers) and with the speaker (Yiannopoulos as a hack troll, known for hyperbole and insult, whose followers often fake tweets as a means of ridicule) would likely not take the fake tweets as real, particularly when he fairly quickly followed up with a mock-surprised "you mean those aren't real?" wink to his fans.
I'm not saying that no court could find otherwise. I'm saying that's the most likely result, and probably the correct one under the law.
Remember: nobody needs free speech rights to protect admirable speech by people we like. It's designed to protect despised speech by people we hate. Yiannopoulos deserves contempt for monetizing bigotry, and his fans are loathsome, but his speech is protected.