They talked about on the radio this morning and according to Cris Carter it was the right call.
When I first saw the replay I was surprised but looking at it from a few angles it appears to be uncatchable because of where Gronk was running to. He didn't try to run a dig route or come back, he just kept running to the post.
Frankly I'm just glad the Pats didn't get an extra shot at that. Carolina was awesome last night and I was glad to see them pull off the upset