I read most of it and your initial assessment was predictably accurate. It's definitely not heart warming stuff, but nothing in there completely shocked me. It's really an unfortunate combination of a guy who is accustomed to acting like a complete a$$hole, coming into contact with a kid who took it a lot harder than most football players would.
You can't help but feel terrible for Martin, but I didn't see anything in there that led me to believe that Incognito was actually trying to destroy the kid. He's just a stupid ma and in his own mind he probably thought he was toughening Martin up. So yes, Incognito is a deplorable prick, but on the NFL sliding scale of bad behavior, I'm not even sure that puts him anywhere near the top of the list.
I'm actually most disappointed that nobody on the team ever stepped up to put Incognito in his place with some of the more blatent stuff. Let's be honest, he may have been the ringmaster of the o-line, but he wasn't the most important or influential leader on the team. Somebody on that team should have put his a$$ down when he started dropping n-bombs (-er, not -a) on the kid and claiming ownership of him.
The whole situation is just very disappointing.