Actually, Japan invaded China during one of the World War II where Japanese basicly kill all Chinese insight and trying to take over.
I think is more of Chinese dislike Japanese because of that history
http://en.wikipedia.org/wiki/Sino-Japanese_War_(1937-1945)
Edit: If the USA never bomb Japan with their Nuclear bomb, China wouldn't be China anymore.. it'll be like "New Japan"
Holy Jesus fucking Christ is most of that wrong.