I agree it was quite cowardly. I'm a huge NFL fan, and this is completely out of character for what happens in the games, so I think it's not appropriate to paint a broad brush with this isolated incident.
I would also say it's a bit over the top to say he should be criminally charged with assault. In that case, Pouncey should also be charged with assault because he threw punches and kicked Garrett in the head. By strict definition, I suppose it would qualify as "assault", but so would every single fist fight that breaks out in hockey, baseball, etc... Boxing (which I am not a fan of) is pure assault by its nature and the MMA (which I dislike even more than boxing) is even worse. They aren't charged. I'm a big racing fan. Fights have broken out in NASCAR many times, and the drivers have...and do... used their cars to take each other out. No assault charges are filed, and in fact NASCAR often doesn't take any action. Sports are rough, sometimes violent. Controls need to be put into place, and disciplines handed out when warranted. But criminal charges are a bit extreme, IMO.