There are a lot of very damning old articles about Cosby, but they predate the internet and you can only find scans of the newsprint. But he was very obnoxious, once sucker punched Dick Martin of Laugh-in from behind at a party, over some perceived slight. He was a very nasty guy off-camera.
I heard a comedienne say something similar about Johnny Carson today. That off camera he was a pretty nasty individual.