The peak of Japanese xenophobia in the 1930s however was conversely very unfortunate for everyone nearby.
Native cultures (however you want to define that) have always shown some curiousity and openness to visitors from outside the culture but that is balanced by some level of xenophobia too, that ramps up as people inside the culture feel that they are being overwhelmed. Both aspects of openness and shutting out are natural traits in any homogenous culture.
You could call the brutal repression of the Ainu and native Okinawans a kind of xenophobic/racist ultra nationalism. Also Japan’s crimes extend far beyond China, and were especially brutal in Korea were they practiced a horrific form of slavery.
The Japanese are so xenophobic they try to exclude the descendants of Korean slaves who have been living in Japan for a century, have Japanese names, and only speak Japanese. Their xenophobia is not laudable.
The broader point that I am making, outside the specific instance of the Japanese which you seem to want to fixate on, is that xenophobia can be a useful social trait, to avoid a society being overwhelmed by a foreign ingress. This could work just as well for the Ainu, the Okinawans and the Koreans (and I'm sure they exhibited it too, but unfortunately weren't in a position to act on it strongly enough to defend against colonisation/vassalisation).
I'm not fixated, I'm pointing out that xenophobia is actually bad and leads to bad things.
I do not agree with your expansion of xenophobia to the behaviour of a people outside their own country. I do not agree that xenophobia is objectively bad. I also do not agree that "the xenophobia of Japan was the seed for a fascist genocidal rampage" and I doubt that many, if any, historians would agree with such a simplistic assertion either.
Since you seem to have a very closed mind on this subject (i.e. xenophobia == bad, bad, bad) and further discussion seems pointless I'll leave it here.