DEFRIENDED!!

So I need to muster up the balls to defriend someone on facebook...and I've defriended people before...but they were people I never actually talked to and they just updated too much...but this person just annoys the shit out of me and makes some comment or instant messages me like everyday...I just don't like him...he's an arrogant, full of himself, know it all, ass...the kind of person when I actually do try to talk to him, just pisses me off more...I can't say anything to him without him trying to one up me or contradict me, or act like he knows whatever I'm talking about better than I do...and when he tries to relate to me it's in such a way that I would want to punch myself in the face if I was actually acting like him...there's no reason I need to let people who make me react this way be part of my life simply for the sake of not being rude...I don't need to tolerate people who anger me just to make them happy, yet I don't want to hurt their feelings...but in a way that just lets them hurt my feelings...or at least give me bad feelings...right?...and I understand that logically, but I still can't reconcile this notion that I owe it to myself to cut these people out of my life with the actions of actually doing it and potentially hurting their feelings in any way...in personal everyday relationships, I DON'T have to talk to people I don't like or make me angry...that's perfectly reasonable...I have a right to not like people, and people have a right to not like me...and I seem to always give in when someone doesn't like me and stops talking to me, and I let the relationship go...with maybe one notable exception...but when someone I don't like likes me, I let it continue...which in a way is worse...but I just don't know how to do it...that's so fucked up...