There's an interesting discussion being had at Stumptown Footy, SB Nation's Portland Timbers blog. Timbers fans have been known to chant 'No Pity' at opposing players they feel are faking or embellishing injury (not at all an uncommon practice amongst supporters groups) which led a reader to ponder a somewhat uncomfortable question; had Zakuani's injury occurred at the hands of a Timbers player, would Portland fans have done the same to him?
It's a conversation worth having a look at. For all that supporter culture has done to advance the popularity of the game in this region, there will be times that the fervor crosses the line of good taste whether or not said line is crossed intentionally. Sounders fans have almost certainly chanted 'Let him die!' at opposing players that had legitimate injuries, likely leading to at least some level of shame when more information came to light.
In any case, conversations like these aren't especially pleasant, but at times they can be necessary. Good to see people having them.