I've never found a reason to actually fight with somebody. It's always better to know how to avoid the situation in the first place. Closest I've ever come was many years ago when I was working as a garage valet on the weekend late shift... caught some guy trying to open our cash register... we grappled for a bit while he was trying like heck to get away and I was trying like heck to get some help... he finally got away, but the cops got him from my description.
Past that defending female friends, girlfriends and my wife... if somebody is doing something to them that they should not be, I've never found it necessary to fight with anyone, but I've been able to quietly convince them that their actions were not appropriate. Bending somebodies joints the wrong way can be an effective deterrent.
