It's always a slippery slope breaking up a fight in today's society. Laying hands on someone in a rough manner can result in a lawsuit against you or your employer if they're hurt in any way during the altercation.
Some people have no respect for anything. I hope though, most of these offenders are either drunk or high when they do this sort of thing. You'd hate to think a rational, sober human being thinks peeing in a public transport elevator is a good idea.
They could use digital technology, like facial recognition type of stuff. If someone who is on "the list" shows up on a MARTA Camera, security is then dispatched to remove that person from the station or transportation car.