It's not intended to be a sport. It's a sort of loosely-scripted drama. It features a bull, whose role is to demonstrate his great strength and speed by fighting well, but is scripted to eventually die, and a matador, who demonstrates his strength and courage by fighting well and eventually killing the bull. (Plus other characters and roles, but those are the central ones.) It is not gladiatorial, because the dice are loaded - the script does call for the bull to die and the matador to live. But it isn't Hamlet either, because we are talking real death and danger. The actors may or may not walk off the stage.
A lot of people have a problem with the bull (nearly always) dying in the ring, because he isn't asked for his opinion on whether he wants to participate. But I'm not convinced that argument really holds water. The bulls are specially bred for the sole purpose of fighting, so if there were no bull fights, they wouldn't even be born. And bulls are mean critters. I bet most of them would choose to fight, if you could make them understand their options.