I saw a guy grabbing girls' butts at a university party. I told him to stop it but he wouldn't listen. I went up to him, tapped his shoulder and told him to stop right now. He looked at me, shoved me against the wall and told me never to touch him again. I told him he was sexually harassing girls, and that he needed to stop right now. He was drunk and he wanted to kick my ass. His friend tried to stop him, and he kept telling him he would get into trouble and that they had to leave. I told him if he kept pushing me I would have to defend myself.
Luckily, security got there before anything bad happened to me, because some of the girls went and told security about the guy. I just stood there and got pushed around and I didn't even need to fight him or anything. I probably would have gotten my ass kicked. The girls thanked me, I went home and ate pizza
I would probably defend a stranger in public again, even if it meant getting my ass kicked. (Plus, I have a baby teeth with no adult teeth underneath, which means it will fall one day and leave a hole. It costs 3000$ to have it filled. However, if it falls due to someone punching me in the face, it'll be free. So yeah)