Question for guys - what is wrong with him?

Firstly I don't think you fully understand what "friends with benefits" are, there are meant to be no strings attached, no emotional involvement. Which this thing between you two clearly has. FWB isn't for everyone and I really don't think it's good for you and your "friend". He's possibly insulting you for the reason he stated or he's doing it because he likes you and doesn't want to get hurt. There's lots of reasons. If I were you I'd rethink what you're doing..