Pretty tough to blame Free for that one, yeah.
Generally speaking, the coaches like Doug Free a lot better than the fans do. Because he knows his assignments and gets in the right place most of the time. He gets beat physically from time to time, and probably more often than the other guys do, but that happens. He's still a middling OT in a league where OTs are at a fair premium. He's a team guy and a well-liked member of the best OL in football. Because he's a whipping boy and the obvious target for the next OL upgrade, he gets more than his fair share of abuse, but that's ok. He'll either move to swing tackle or off the roster next season, and we'll be able to replace him without all that much trouble.
All in all, he was a good value for a 4th round pick.