I would hardly consider China "Marxist" even under Mao. It was nothing more than state capitalism. Sure, in some ways it was a big improvement over feudalism and China did achieve rapid industrialization, but it was in no way coming close to building socialism. Beyond that capitalist China still continues to occupy Tibet and they are in no way "Marxist."
Furthermore, (and this may not necessary apply to you, I don't know) but I've noticed a major double standard when it comes to some communists and China. They will all criticize the U.S. for invading Afghanistan and Iraq (and rightly so) yet when China invades Tibet it's fine. When current capitalist China continues to occupy a country that doesn't want them there, many Communists support China, but oppose the U.S. doing it in Afghanistan. This is modern capitalist China they are supporting, mind you, not Maoist China And why? A lot of their answers are the same reasons some Americans support the continued occupation of Afghanistan because it's a backwards theocracy. It's the height of hypocrisy to oppose imperialism except when it waves a red flag. Some seem to hold the view that American Imperialism is bad, but if China does it's okay, because they claim to be socialist. Either oppose it or don't, but China has no more justification for the continued occupation of Tibet than the U.S. does for Afghanistan.
Once again, this may not apply to you, but I've noticed in on several websites and forums.