It's bad to say mean things about someone's sexual preference.
William was offended at Michael, because Michael had said something mean about him.
William wanted to pay Michael back for the insult.
William told Michael what he really felt about him as a person, how bad he was.
Wlliam started right away calling Michael gay, and other insults for his sexuality.
Michael split from him, and he never heard from him again.
Michael told their friends about it, and all of them had a lower opinion of William.