Island mentality refers to the notion of isolated communities perceiving themselves as superior or exceptional to the rest of the world. This term does not directly refer to a geographically confined society, but to the cultural, moral, or ideological superiority of a community lacking social exposure. Island mentality can be characterized by narrow-mindedness, ignorance, or outright hostility towards any artifact (concept, ideology, lifestyle choice, art form, etc.) originating from outside of the geographic area inhabited by the society.
So you're saying the Japanese are stupid? I'd rather be a narrow-minded ignorant fuck who preserves and develops a unique culture, than a whore intermingling with every outside influence and losing any and all uniqueness.