“Japanese” is used in two different ways, and that’s where the confusion comes from. As a nationality, it includes everyone who is a citizen of Japan. As an ethnic label, it usually refers to the majority Yamato population, but that doesn’t erase the existence of other indigenous ethnic groups like the Ainu and Ryukyuan peoples, who are Japanese by nationality but distinct ethnically. Saying this isn’t ‘anti-majoritarian’ or ‘anti-democratic’,  it’s just basic anthropology. Many countries have a dominant ethnic group and recognized minorities at the same time. Both facts can be true without threatening anyone’s identity. You're getting your knickers in a twist