Sarcasm seems funny when we do it, but it seems mean when it is done to us. To onlookers, sarcasm seems funny or mean depending on which side we identify with; and it is illustrative that we so often side with the aggressor.
Oxford informs us that sarcasm means: “the use of irony to mock or convey contempt”
To mock or to convey contempt; even the definition tells us that this is a hurtful style of humor which is to be avoided. And should we need any more persuading, the word sarcasm comes from the Greek sarkazein which translates as tear flesh.