Mia Farrow and her son wrote a scathing attack on China's Darfur policy for the Wall Street Journal and, adhering to my belief on the need for a catchy title they use "Genocide Olympics" (the article can be found here, subscription only).
The IHT did a far better job examining China's policy in Africa a few weeks back, though I can't find the article right now. China's current trade policy in Africa is frought with problems because of its lack of morality. They are willing to trade with anyone and everyone, no matter that nation's domestic politics, as long as they have something China wants and are willing to not recognize Taiwan, China will trade with them. This has led to some embarassing trading partners and situations, including currently trading with the Sudan. China's foreign policy generally lacks "morals" in the western sense because, recognizing China's own domestic situation, they refuse to pressure or influence other nations in their domestic situation. By taking part in the 6 party talks and pushing North Korea, this is probably the most China has done to "push" another country to change its domestic politics.
If you want to defend China, you need to get your shield ready. With less than 500 days until the Olympics, there will only be more attacks on China, its policies, and whether it legitimately has a right to host the Olympics. What the Farrows are doing here is unfair, but we are bound to see a lot more of it. What has the US done in Darfur? What has any country done for them so far? China trades with the Sudan, but that doesn't make the government a Chinese-backed one. There is no UN embargo on trade with the Sudan and the US, UK, and many other nations still trade with it. I don't fully agree with what China is doing, but the focus should be more on one's own country (especially when that country is doing nothing), instead of attacking another country. However, attacking China and its right to host the Olympics is a good way to get an article published instead of attempt to create real discussion in the US on the issue.