That was not a good call, imo. They didn't have a grasp of what happened. It was one of those "let's congregate and decide if we should make the call after the fact or not". If you don't see something clearly enough to make a definitive call immediately, then don't make the call at all. Pierce didn't throw a punch, didn't try to hit the Pacer, didn't knock him down. The Pacer flopped (clearly). Finally, the refs were trying to influence the outcome of a playoff game on a wishy-washy call.
Bogus. That's the type of situation where referees need to be definitive one way or another. If that was one of our players, we'd feel a lot differently.
Just because Pierce would've had more common sense to stand there and not move at all after getting hit in the head, it doesn't absolve the refs from making an improper call.