I think "I Statements" work only in cases where there's a mediator, to be perfectly honest. Because then you have someone sitting in to move the conversation forward. Otherwise, there's really no point - the subject of the "I" statements will either talk/bully right over the speaker or will be insulted (specially if it's a friend, that's what happened to me), making a bad situation even worse. And even if there is a mediator, who's to say the bully won't just pretend to have accepted the session and go back to their ways as soon as it's all over?

Stuff like this makes me want to go into teaching just so I can be the cool teacher who actually knows how to give advice. But I'm otherwise not that interested.