Even if 99.9% of the Japanese had behaved in such a way (and I know the numbers were nothing like that), each individual is responsible only for his or her own actions. Most Japanese today would find those actions horrible, but even if they don't, it doesn't change how any single person should be viewed.
Racism is a vile thing and hating someone for something they personally didn't do and may not condone is a violation of everything the gospel represents.