It's probably cheaper to have a trashcan onboard than an armed driver. Yes, when you threaten people with ejection sometimes they threaten you right back.
If people don't respect what the driver says, the driver should stop the bus, and call security and then not move until the issue is resolved. There should be no tolerance at all for people that threatens the driver.
And all of this could have been avoided with a trashcan on the bus.
If you've watched anything on youtube you'll see that people escalate a situation for some of the stupidest things. The world is full of crazy people and they drive or take the bus too.
Where does that happen?
There are many cities where you can enter through any of the bus' doors.
I'm not sure when they would clean a bus though. I'd rather have my bus driver drive than stop to pick up rubbish.