Ellis was fined by the league for throwing snowballs at Seattle fans. This was after about an hour, in the fourth quarter and after the game, of Jets players, coaches and officials getting bombarded with snowballs, and the Seattle officials essentially doing nothing about it.
So Ellis, who is a very fiery cat (and the Jets need more like him), had seen enough, and he fired back.
If the NFL is going to fine Ellis for doing this, than the Seahawks should be fined as well. Or maybe Seahawks owner Paul Allen should do the right thing and pay Ellis' fine, since his organization did nothing to stop the snowball throwing.