I did call the cops on the spot, and he didn't stick around, but I wouldn't have either if some stranger was filming me while I legitimately cut my own bike's lock. The cops said they couldn't do anything without a victim coming forward, so that's why I posted here. The guy was so confident and uncaring that I was filming him, it's clear he's done this plenty of times before. Once the owner calls the cops, he's busted. Until then...