Herron's elbow wasn't seen and Kljestan's tackle wasn't punished with a card, yet the disciplinary committee suspended Herron four games and Kljestan two. And these punishments were justified: Herron clearly cocked his elbow and swung it into Heaps jaw; Kljestan's tackle was an attempt to win the ball but he clearly slid into Williams from behind and caused an injury serious enough to sideline the RSL attacker for at least a month.
MLS rules prohibit the rescinding of cards except if the referee misidentifies the player being disciplined. In that case, it will rescind the incorrect card and transfer it to the player whose name/number should have been taken.
There's certainly an inconsistency inherent in punishing players but not rescinding cards after the fact, but the decision to caution or eject a player is a judgment call, like so many of the decisions referees must make. Perhaps Vaughn saw the Joseph tackle from behind, believed that Joseph had stuck his outstretched foot into Ben Olsen's from the side or thought Joseph had gone over the ball.
Actually, Joseph lunged in front of Olsen and the ball, perhaps anticipating a dribble or pass forward. Instead, when Olsen cut the ball to the side, Joseph either missed it entirely or barely nicked it as Olsen's momentum carried him forward and he tripped over Joseph's leg, as in singular, as in Joseph did not fly in with both feet.
A foul had to be called but nothing about the tackle could be deemed cynical nor violent. Joseph did not clip Olsen's heels as the D.C. midfielder went past him, which would have merited a caution.
Vaughn's awarding of a penalty when Jaime Moreno was shouldered off the ball by James Riley also drew criticism. The players were running side-by-side as a ball rolled into the penalty area and Revs keeper Matt Reis came out to collect it. The contact was shoulder to shoulder and not violent, but Riley, who had inside position on Moreno, did raise his arm somewhat and Moreno crashed to the grass.
Only a severely stretched interpretation of the rules could deem this to be the use of "unnecessary force," the only possible criteria for a foul to be called, as Riley didn't elbow, grab, trip, or impede Moreno. The ball was within playing distance and thus players are empowered to shoulder charge each other in their attempts to control the ball.
Moreno is certainly one of the more adept divers in MLS, perhaps in retaliation for all times he's hacked and grabbed and kicked. This was a tough, scrappy, hard-fought game and Vaughn, one of the top U.S. refs, tried to call it close yet not too tight.
Top-class attackers should be protected by the referees, but they shouldn't be gifted, and in this case, Terry Vaughn played Santa Claus.