Homogeneity isn't achieved by being open and welcoming to difference. Homogeneity is a path of cultural evolution that did pretty well for the Japanese over time, it kept them isolated from western interference during times when a large part of Asia was under the heel of western powers, they were even kicking the Russians asses when Europeans still viewed Asians as people who couldn't competently govern themselves. Some kind of Japanese exceptionalism fueled the imperial conquests of a significant part of the Asian Pacific before and during WWII. The treatment of the people in their colonies was a brutal and inhumane as any empires behavior in modern history, you can't treat people that way if you look upon them as people equal to yourself. Just because we bombed them into pasivity doesn't mean that we destroyed their cultural DNA. Makes me think of of how Orwell talked about the difference between himself and the natives in "Killing an Elephant".

I know that Japanese people descended from the untouchable class still try and cover up their ancestry to avoid discrimination for jobs, schools and marriage, so while being from the Samurai class may not carry the weight it used to being from the bottom of the pile still matters.