What "parachute" are you talking about?
NYSE only busted trades in 6 of the 140 securities Knight effected. And those 6 were only busted because they traded 30%+ off of the market open price. Which is well within NYSE's normal tolerances for approving busts. (Now if busts should be allowed at all is another debate.)
Knight had to pay for all the rest, and it nearly closed the doors. The government didn't rescue Knight, the street did. The industry pooled a bunch of money and bought a huge chunk of Knight in exchange for that money. That purchase obliterated existing share holders. Sounds like everything worked fine to me.
Knight made a mistake, and they paid for it. What more do you want?