I just had a thought: when you walk through the downtown of most US cities, you see and hear a lot of "street preachers," and as far as I know even Christians find them pretty annoying (especially when they link their sermons to legalizing marijuana, as I have noticed is often the case). The other thing you tend to see is enterprising musicians with a hat in front of them.
Just about everyone loves the latter, most extremely dislike the former. Extrapolating to your situation on the bus -- what would you have done if some traveling musician had gotten up with a guitar and just started playing? Is it about the "being taught at" aspect, or the "disturbance" aspect? There are different levels of presumption involved.
EDIT: damn, I can't tab+enter to submit comments anymore on you guys' mirrored posts :p
That's a good point flag. Would I complain? It depends on the music I guess, or if I was napping. Music may not bother me. A lecture at the front of the bus on the wonders of the Ontario countryside might not bother me but it might bother someone else. The 80 people on the bus were a captive audience. If anyone complains, the driver has to fulfil the company's promise to the passengers: a ride without disturbances. The annoying thing is that she did not respect the bus driver's request and kept talking when he asked her to stop. If someone complained about the music and the musician kept playing, I imagine he'd get turfed too.