China is becoming a world economic superpower. The economic output of China is the second largest of any nation on earth. As such, China is a trading partner with many other countries around the world. Because of their position in the international economy, they should be WTO members to improve trade relations.
China should be allowed into the WTO since to leave it out would further isolate a nation-state which is already creating tension in the Asian region. China does engage in questionable trade practices at times, however these can be better fought through cooperation rather than keeping it out of the organization. For example, if China is in the WTO, sanctions within that framework can be sought. Outside of that framework, the possibility for sanctions is essentially nil.