I found the original thread. It is an r / news thread about the "far right" Sanseito party "shocking gains" in their most recent election. Predictably, because of course it is in r / news, it is full of redditiots who cannot see the real root of the problem.

Japanese people want Japan to be Japanese, not Somali, Han Chinese, or Vietnamese, or whatever other migrants come to their lands. Thanks to social media everyone can see what is happening in Europe, Australia, and the US, and they don't want that in their homeland.