This. Hell, just what Norman does in this story arc is screwed up and unforgiveable - basically brainwashing Peter - let alone what he's done before. I don't think Jenkins is trying to say "oh poor Norman let's all forgive him because of the abuse", and frankly I have no idea where people are getting that, but I appreciate the attempt to flesh out Norman's backstory.
After all, things must have happened to make him the maniac he is today. (I have never bought "oh it was just the Goblin forumla" -- THAT is a copout.)