I've never been in a situation where I've ever been in a physical fight with anyone in public, but I did have two instances which come to mind where I almost was in a fight in public:
1) I was at a club in my uni town (small city of 30k) chatting to a mutual friend while my friends were in the toilet and a bunch of rugby lads who were interested in her and she was ignoring and about 8 guys started shoving me to try to impress her when she got confused as to what I said because the music was super loud and made a face. While this was happening both of us just looked at each other like "uhhhhhhh wtf is happening rn?" she said "WTF are you doing?" "He's making you uncomfortable" "No he's not. We're just talking. You guys are the ones making both of us uncomfortable" and then they preceded to act all buddy buddy with me which we both were like...... um no.
2) I didn't see this happen, but my flatmate did. A girl was about to fall off the state at a club and I grabbed her to prevent her from falling and she gave me a hug and I said "You're too wasted to be that close to the edge," then we both laughed and she moved along. However, while this was going on my flatmate had a conversation with her boyfriend who wanted to fight me for 'touching his girlfriend' and my flatmate said "He's gay & she was about fall 3 feet onto the floor" and his response with "I don't care. I'm about to beat the shit out of him" and my flatmate shoved him grabbed my arm and said "We need to go" and dragged me to the bar for more drinks. Like bro maybe if you were a better boyfriend a gay guy wouldn't have to help your girlfriend from getting a concussion at a club lol.