Who made this quote?

Who said, " man's inhumanity to man..." and what are the missing words?

I Googled "man's inhumanity to man.."; and though I did not discover who made the observation first, I found the advertisement in the right-hand column most illuminating. It said, "INHUMANITY For Sale. Low Priced Inhumanity. Huge Selection at eBay!"

man's inhumanity to man never fails to shock me... neither does capitalism.