You cause a scene on a plane, get arrested and banned from flying for life. Why don't we have a zero tolerance policy for public transportation? If you litter, banned. If you eat drink or smoke, banned. If you steal or assault other passengers, banned and your duck taped to the seat. Bar bad people from using public transportation, make them walk, make them feel alienated, let them not be able to travel freely. If they complain about it remind them of why they shouldn't be allowed to travel in the first place.