I think you are wrong that most side with the billionaires. It would be an interesting poll.
I can only tell you my take. It's a matter of "principal", in this particular case.
If X were being seriously underpaid, and nearing the end of a contract, I wouldn't have any issue, whatsoever. Here though, he just got a new contract, that apparently suited him fine at the time. Now he, almost immediately, wants a new one? Because he feels slighted that Jones got what he could? It appears to be pride driven, as he has already gotten a huge deal. He isn't drastically underpaid. If he had a bad year, or ended up on IR again, would the Dolphins be in a position to restructure? Heck no. Not given the signing bonus, and gaurantees involved.
I try to look at it from both sides of the negotiating table.
No. That sets a bad precedent.