During last night's game vs Knicks, when Carmelo committed his second foul he brushed against the ref and was saying things that was getting the Ref pissed off. Compare that to Rondo brushing against the ref and telling a joke.
Rondo gets suspended a game and nothing will happen to Carmelo unless they get him for his after the game activities.
It seems that the league has a prejudice vs Rondo. Especially, since Rondo was wrongly called for a foul on the play when it was a foul on the defender. Also with Carmelo, Heinsohn predicted they would all a bogus foul on Pierce right after that and they did 15 seconds later (which put Pierce on the bench with 2 bogus fouls)