As long as one is generally aware of slavery and the multiplicity of other such crimes against humanity, I don't really see that the specific knowledge that Amazing Grace was written by a slave trader, or that the operatic tetralogy, The Ring of the Nibelungen was written by a person who, among other things, was anti-Semitic does anything of value. Newman and Wagner are both dead. Focusing on the unadmirable characteristics of these two people doesn't decrease slavery or anti-Semitism in any way.

The only thing such a focus accomplishes is that it taints one's own enjoyment of otherwise fine works of art.

Don Firth