This song has so endeared itself to many people that its origin is likely of little consequence to most of them. I am certain that there are other examples of works created by men of less than noble lives and deeds that transcend those roots, so long as the works have redeeming social or spiritual value in and of themselves.

You could look at it, assuming you are a religious person, as the Lord pulling good works through the least likely of channels for reasons known only to Him (or Her?).