I'll say this some time and someone will tell me I'm an idiot for quoting some awful person, but right now - not knowing if it is a quote or not - I love this
I've always thought the value of quotes (when they have any) is based entirely on their content rather than who spoke them. A smart quote from an awful person is still smart. And a dumb quote from a smart person is still dumb, like that definition of insanity one that often gets attributed to Einstein.
I'm sure there's some sort of logical fallacy to be said about negating the quality of a quote based on the person who said it. Like, if Einstein said it, then it must be smart. If Hitler said it, then it must be evil. Etc.
Seems like the first use was in a life magazine article by someone who didn't want to take explicit credit, so chances are it was something thought of by his students. And then it was repeated by various comedians over the years.
For what it's worth, my quick skim of the author, William Sloane Coffin's wiki makes him seem like a pretty great guy.