The argument did nothing until last year proves nothing. The rating is solely based on the latest data--the last year. Every player will have an initial year of grading high.
It seems that your issue is more that you disagree with the importance of the player to the team. Look at Mo Alexander as an example of the importance of the high safety to Wade's defense. I am one of Sammy's top fans and a big believer in the dramatic positive effect he had on the offense--stats be damned. Did they sign the right guy? I dont know. But I would hate to lose LaMarcus, and I hate losing Sammy.
The rage at PFF is curious to me. They attempt to quantify something very difficult so that relative assessments can be made. Looking at their ratings in a general way provides the most value This player is good or this player is bad. Not this player is number 4 or this player number 26. People seem to take the PFF rating emotionally if they disagree with their opinion.
Very few people here have the patience and the desire for truth to look at the film themselves. PFF at least attempts to do this for you.