An Eminem Question...?

I know this is an old song but I just recently listened to his diss song to Mariah Carey and Nick Cannon (her husband) about warning them and her not to denied that they had a relationship,my question is why did Eminem has make this public and embarrass them,yes I know Mariah did "Obsessed" but didn't he started the whole thing first,why does he has to go and diss her in a song,he can't just be a gentleman for once and go and deal with it in private. Serious answers only please!