I'm sure Carroll knows by know (especially after a move away) that Newcastle fans always expect the right stuff to be said, so Nolan going out and saying that it was a great move for Carroll, and he's joined a massive club, makes Newcastle fans clearly angry because they're a big club.
I know their friendship won't be damaged, it's just if I had a mate who had gone on to better things, I wouldn't apologise to people who look up to me because I wished him the best.