real reasons for anti-semitism
It's bigger than 'nasty Jews' or 'nasty Gentiles'....
Jewish values are, in some ways, a bit comparable to Gypsy values - maintaining group cohesion against a hostile outside majority is very important. This also requires ascribing negative attitudes to outsiders even when they might not be present.
This requires a delicate balance of irritating the majority but not enough to bring about serious reprisals and rigorous record keeping and the nurturing of grudges.
For a time (1950s-1980s give or take 5 or so years) non-Orthodox Jews were more interested in integrating into broader American society even celebrating the secular parts of some holidays. Then starting in the 1990s (roughly) it seems they decided that was a threat and they have to differentiate themselves more. Bye melting pot and welcome ethnic free-for-all.
I'm wondering if that coincided with (or was partly caused by?) the manifestation of strong anti-semitic feelings among more radical African Americans, which maybe debuted on the national stage in 1988 with Jesse Jackson's "Hymietown" remark (that was the first I heard of it at any rate).