The tendency of a subsection of orthodox Jews from one area of Eastern Europe to self-ghettoize is something of a red herring. In Western Europe, Jews were never truly integrated unless they converted. And even those who converted and their mixed race children were ultimately slaughtered for their ethnic background, giving lie to the notion that even a WWI veteran ex-Jew could become German.

The Haredi (ultraorthodox) movement itself is a reaction to urban Jews who wished to assimilate when such a thing became conceivable in the 19th C. And this is a ghetto mentality. In American terms, your question would be equivalent to "which Black people?" Implying that people who claim and cling to ghetto culture have a hard time integrating. But that 1. dismisses the role that ghettoization had on creating a subculture in the first place, and then 2. pretends the subculture itself is the reason for failure to integrate, i.e. that it's the cause rather than the effect, and 3. serves to allow and excuse and justify the mainstream of society projecting their negative perceptions of that subculture onto individual members of the same ethnic group who would like to integrate without completely renouncing their unique heritage. And in the Jewish case, even complete renunciation wasn't enough, so perhaps the ghetto culture had a point.

To antisemites, the type of Jew is not relevant.

I take your point though. Even nominally homgenous societies will stratify and have out-groups.