The Chinese government is sensitive about Avatar not because of its Western resonances, but because of specific plot points that are important in the Chinese context: mainly, the idea of natives driven off the land by arbitrary fiat in favor of corporate development. It's a common practice in China these days, and probably one of the biggest issues that causes open dissent in China (actual people-on-the-street protests and legal campaigns against government decisions, not just publishing stuff the Party doesn't like)
And now on to wild speculation: my guess is, they pulled it from 2D and not 3D because the kind of people who have actually lost their land to government-backed development schemes are poor peasants (or newly-minted migrant workers) who aren't going to spend the extra money on fancy 3D movies. To the urban middle class that'll pay extra for the 3D experience, this movie's plot is just as meaningless as it is to an American or European.
As far as the laws of mathematics refer to reality, they are not certain, and as far as they are certain, they do not refer to reality. -- Albert Einstein