This would take a very long answer. The short answer is that racism is everywhere. The Cambodians disliked the Vietnamese, for instance. To really get at your question you need to look at how modern China developed from the Silk road to the Mongol invasion and the forming of the People's Republic. This modern centralized power seeked to gain influence using tactics that were none too friendly to their neighbors.
Also, there is a difference between disliking the Chinese people and the Chinese culture. I can not tell from your stem which (or both) you refer.