To be fair, if that is how it happened, sounds like he didn't do anything wrong. We've all made jovial comments like that. Those of us that are commuters will know bits of humour like that are needed to remain sane!
If a bus driver told me to get the back of a queue for no reason, I'd have given him a mouthful too.
The whole thing could of been avoided if the driver hadnt been so rude and abrupt on opening the doors. You obviously was not there otherwise im sure you would have a different view. the reaction of those at the front to the drivers welcome so to speak was one of disbelief.
I was simply being glib.
I remember heading to the bus stop to get the bus home after school, got in line, got to the front went to get on, showed my ticket and the driver said he wouldn't let me on because "you shouldn't use language like that". I was walking alone and hadn't said anything.