The Packers, Bears, Raiders, and Saints all did the same thing as the Redskins and Cowboys. They restructured bad contracts to move the bulk of the cap hit into the uncapped year. The Bucaneers and a few other teams also took advantage of the uncapped year by going under the normal floor of the cap.
In fact, what the other owners/Goodell did was illegal. As part of the agreement that kept the season alive leading up to the lockout the NFL told the NFLPA there would be an uncapped year (something the NFLPA would really like) but they then went behind the NFLPA's back and told the owners that if they went over the non-existent cap they would be punished. This is collusion and it is illegal even in an industry with an anti-trust exemption. Part of the reason the NFL can get away with being a monopoly is the CBA with the players. Violating that CBA by making agreements counter to the CBA behind the players back is illegal. The reason they didn't want teams to go over the cap had nothing to do with competitive advantage. They didn't want to give the players extra cash right before the lockout.
The punishment wasn't about competitive advantage. It was about Goodell saying, "The old money owners (owners like the Mara family, Rooney family, the Halas/McCaskey family [oh look, a team that did the same thing as the Skins and didn't get penalized.]) and I rule this league. We do what we want and you fall in line or you get hammered."
And Jones is a better owner than Mara. Only ManU is worth more than the Cowboys. They both won their Championships when they were lucky that they had HoF QBs. Difference being that Jones drafted Aikman (and made the Walker trade that made them a dynasty) and Mara got lucky that Manning wanted him.
Also, the arbiter isn't exactly as impartial as he is supposed to be. He basically works for the NFL. Finding things in the league's favor is necessary to have job security.