A few times. Three guys from my local rugby club were drinking in the bar I was working in. I was there, but not on shift, I was waiting for my friend to finish her shift. One of the blokes knew me vaguely via my brother but the other two didn't. A customer kept spouting misogynist stuff to my friend, getting gradually louder, until one of the blokes heard, and shouted "Oi, muppet, keep your village idiot ideas to yourself!" Another one chimed in "That's my sister you knobhead, " All three of them stood up, and turned to face this customer, and he slunk out.
Was lovely to see.