I think the league would be heading down a very slippery slope if players are expected to "sell it" in order for a penalty to be called. What you are doing then is encouraging flopping; if that's what you want then watch soccer, or even NBA basketball.
When I initially saw the flag being picked up, I actually thought it was the correct call. It was only after watching it in replay that I felt otherwise; Kuechly made contact just threw yards deep, and pushed Gronkowski back.
In terms of 'selling it', perhaps Greg Olsen should be fined for his embellishment. I haven't re-watched that play yet but in real time it seemed as if Olsen was actually holding McCourty's arm with one hand to give the appearance that McCourty was guilty, and then throwing the other hand up in the air to draw the attention of a referee.
All that being said, to me the most critical play was neither of those, nor Ridley's fumble, nor Newton's scramble, or even the touchdown by Ginn; it was the third and one inside the ten yard line when Blount was running the ball well, and they decided to pass. I just did not understand that play call.
For the record, per the NFL Rulebook that final play should have been defensive holding.
NFL Rules Digest: Use of Hands, Arms, and Body
The defensive player cannot use his hands or arms to push from behind, hang onto, or encircle an eligible receiver in a manner that restricts movement as the play develops. Beyond this five-yard limitation, a defender may use his hands or arms ONLY to defend or protect himself against impending contact caused by a receiver. In such reaction, the defender may not contact a receiver who attempts to take a path to evade him.
