Why do men defend women even when they're wrong?

After personal experience as well as ..well, seeing things on TV and whatnot, I've come to realize that no matter how stupid a woman may be acting, there will always be some white knight who feels the need to defend her despite her behavior, even if it's just from someone telling her off or putting her in her place. I was watching a movie (I can't remember which one,) and the woman was whining about a bad food order. She started making a scene, screaming profanities at the waitress, throwing her napkin across the room, and when the (male) restaurant manager came out to explain that her behavior was unacceptable and whatnot, this, for some reason, really aggrivated and upset her boyfriend, who stood up from the table and asked the manager to speak politely to the "lady'. Do they ume that they're going to get a lay out of the deal or what? Is my boyfriend the only man who wouldn't put up with my acting like an immature spoiled brat? Sorry but it's a pet peeve of mine.