Your problem with the line "how many ears must one man have", john f, is this: you are being too literal in your interpretation of it. It's a poetic metaphor for a person's overall moral and ethical awareness of other people's suffering, not his ability to hear out of one, two, or more physical ears.

There is nothing wrong with that lyric or the song it's in. It's one of those rare songs that is just about perfect.

If you want to pick on Bob, look up the words to "Wiggle, Wiggle". Really quite unusual. ;-)