Being butthurt means being aggravated, pissed off, or bugged over something completely trivial. Usually when people are butthurt they are really dramatic about it. Most people like to laugh at or even mock the annoyance of butthurt people because their reasoning for being so butthurt is ridiculously stupid.
Guy 1: Typical Chandler is butthurt again about us drinking one of his beers and hiding his bike.
Guy 2: Yeah, he was really butthurt last night when he lost beer pong and I called him a little bitch.
Guy 1: When will Chandler ever learn to take a joke?