To play a little bit of devil's advocate here (and I've really come to hate Cam by the way), there is a message about "defending the house" that I know players have taken to heart down there. It's based on what happened with Ron Rivera's house burning down and the message that he delivered to them in the aftermath of that. I know his players took that to heart and in this case, Newton took it too far.
May I just say players, especially when unprovoked should not be anywhere near where the fans are, other than to do a TD celebration by leaping into the end zone stands. I mean they shouldn't be when they are provoked either, but especially not this. And what he did should be condemned and fined for.
Now as to the fan, I don't completely get how a sign should need 500 bucks to pay for it, esp when it seems like you could make a quality sign for about only 50 bucks or less. I mean you'd have to put in the time to do it, but sure seems like it could be done. That's about a month's rent in some cases so, word to other fans please do not spend $500 on fan gear.
But still, Newton has no right to do that in a game and he needs to eat a huge slice of humble pie this year for that.