That's a pretty simplistic perception of the NFL...
Ross did what he was supposed to do (on this particular play). As earthsci mentioned, the tackle doesn't decide his action the play call, the audible and the line call do.
As far as a RB blocking a rushing DE... the play was designed for Lienart to move to the left, i.e.- it was not a straight drop back pass. (That contibuted to the fact Matt never saw the DE coming. ) Edge missed the call and went the other direction. Had Edge picked up the call and moved to the right to block the DE he doesn't have to stone cold stop the DE, just delay him because Lienart would be moving away in the opposite direction.
Regarding Green stating Ross missed his block... I hate to think it but again that fits DG's MO, sticking up for "the star" player (see: Minnesota/Moss)
