From the refs perspective in real time, I bet that it looks like an aggressive end to the play but probably not flag worthy. As a Packer fan, I was mad and so obviously was Jones. The player made the initial tackle inside the endzone and continued taking Jones down to the ground and twisting after he had pushed Jones outside of the endzone. Certainly it was overzealous and dripped with desperation anger, and I hope that the league imposes a fine.
I understand why the refs may have declined to throw the flag, but in a game where temper tantrums were mounting on the Cowboys side, a well-deserved flag would have demonstrated to the players that this behavior would not be tolerated as the game continued.
Hopefully karma gets back to that DB (and that isn't an acronym for defensive back)