Why was Twitter so vague about banning Milo Yiannopoulos?

Last night, Twitter banned one of its most infamous users: the Breitbart editor and conservative pundit Milo Yiannopoulos. In a statement sent to Recode, Twitter said that while "people should be able to express diverse opinions and beliefs on Twitter ... our rules prohibit inciting or engaging in the targeted abuse or harassment of others." A screenshot posted to Breitbart said much the same thing, adding that the account was being banned permanently because he had been given similar warni