Facebook ethics.. Is it pity to unfriend an ex on facebook after he broke up with you?

[Paris]

Our break up was very painful for me because he dumped me after 2 years having a great relationship, giving no specific reason. I'm still feeling very hurt for not knowing what happened and why he turned to be totally different person than i known. We are still friends on facebook, have a lot of mutual friends as well. but having him there seeing him all happy chi chatting, liking, commenting on all our mutual girlfriends hurts me so much.. i dont want to act irrational and show him that im very hurt. but need some advice on how to handle this right now. He has also been chatting and commenting with an a ex-friend of mine recently..a friend who back stabbed me and he knew it all about it..please tell me what do do? i dont want to make myself look immature either.. NEED YOUR HELP.