Once again, like most things, I think people jump to extremes where the reasoned reality is somewhere in the middle.
What he did was bad. To yell that at someone in anger, in 2013, from someone as young as he is, that come from a bad place within. To me, that's different than Paula Deen being meta-racist because she talked about one time in her life in 1987 she said the N word. It's different from Zimmerman acting in self defense and race being artificially injected into a situation where it didn't exist.
He should and will lose the respect of his teammates, fans, and employers. The Eagles are even justified in fining him. I don't think any amount of "sensitivity training" can make you not racist, so in my opinion, that's silly. Should he be dismissed from the team? I think that's extreme. Is this worse than Michael Vick mutilating dogs or Ray Lewis being involved in a homicide? Of course not. The faux shock and disgust is wearing thin.
As for discussion of "N-word" itself. Again. Middle ground. It's silly that you have to say "N-word" instead of just saying it. We're adults. It's like a kid saying "the B-word" instead of butt. I can just come out and say fuck, mommy part, faggot, chink, jap, spic, etc. but I'm not comfortable saying that word.
On the other hand, it's just the way it is and it's similarly childish to want to do something just because you're told you can't. Get over it. It's ok for them to, just like it's ok for you to talk shit about your sibling, but no one else can. It's just the way it is. It's not rocket surgery.