I had a situation thrust upon me somewhat like this many years back.
I was a wee lad, back in the old country, when.. oh wait, wrong story.
I was a high school senior and I was hanging out at a basketball court, waiting for a friend to come by so we could see a movie, and this chick, who I had a class with, and her bf, who I knew of, but not personally, started having an altercation. I didn't know either of them well out side their name, but the chick knew who I was. So I'm leaning against my car by the bleachers, when this dude starts to get rowdy. The dude was drunk and like 22, but I knew who he was, because he had two brothers in the high school. The trio were known as the Dixon brothers. I start to look around and I notice that no one else is there but us three, and this dude is effin big. He's explosive, rowdy and drunk, so nothing is look good for me. I suppose I could have walked away because the girl didn't ask for me to intervene, nor did either of them really acknowledge I was even there. But regardless, I saw where the situation was going, and I let out a deep sigh to myself. I can still remember vividly how I bent over, and re-laced my shoes really tight, emptied my pockets on the ground, and prepared to get my ass whooped. I was so damn mad that this had to happen, and probably more mad that my friend was late, thus resulting in me still being here to see this unravel. Again, the girl never asked for any help, but I couldn't sit there and do nothing any more. Sure enough, as I finish my prepping, he puts his hands on her, grabbing her and slamming her against a nearby chain-link fence. So she yanks her hands free of his, and at this opportunity, I appear out of nowhere between the two of them, like the dark knight, and much like the dark knight, I grabbed him, and spoke the immortal words of "hey man, be cool." But this guy, much to my not surprise, apparently did not want to be cool. He looks at me like I just told him 2pac wore high heels, and his mama had a peg leg. The girl says nothing as I do this, apparently content to watch me take the beating. He yanks his hands from me and utters a few expletives about getting my hands off-a him and starts walking toward me. At this point I'm ready for my ass whooping, but at least content that no one was going to see it, and that worldstarhiphop would not be invented for at least another 13 years. He continues to move forward, apparently too drunk to throw a punch, instead opting to try and grab me and tackle me to the ground. This is before I learned any jits, so I didn't try to jump guard as much as I tried to guard my junk. Fortunately, and miraculously, some people came out of the nearby apartments, one of them his mom, and she called him in and he left. The girl never said thank you to me, or anything at all about the situation. No one at school or anywhere else ever knew what I did, but I did feel kind of special at the end of the day.