Talking of ignorance, is that a dance tune rather than a song tune? It's quite in order for a song tune to have an A part and nothing else. If someone makes a song, they might decided only to use part of an existing tune.

As long as it's clear you mean ignorant in its literal sense you're on safe ground; if it's clear you mean the "bad manners" sense, that's fighting talk!

BTW, slight digression ... There's a very entertaining story by the writer Saki involving a little boy singing On the road to Mandalay, and that line is all he knows. You'll probably find it on-line somewhere.