Yes, that's understandable. The exclusive and long-outdated attitudes would have been a mystery to most traditional singers in my experience. The early collectors had some excuse for their selection in as much as a number of the songs were to be found on street literature on sale up the road, however, the second revival has no such justification. I can see how Bob would be dis-chuffed when one of the nameless (who also changed his attitude quite dramatically in later years) shouted at him from the floor while he was singing.
By the way, I witnessed Bob returning the compliment in London many years ago. Hilarious!