Besides White Nationalists and some Muslims who actually engage in full blown anti-Semitism, one of the biggest groups of Anti-semites are themselves Jewish.
There have been many articles written characterizing Jewish critics of Israel, like me, as self-hating Jews, and I've been called that many times. Some articles, like Michael Laitman's, in The Times of Israel, even suggest that Jews who criticize Israel and Zionism have become haters of not just Israel, but the Jewish people. Laitman inappropriately conflates criticism of Israel and Zionism with hate of the Jewish people.
I would argue that Laitman's assessment is actually anti-semitic for a very ugly reason. He can cloak his rationale in a shallow reference to the Talmud, but he is actually attacking the majority of American Jews because they are progressive and they are unhappy with the policies of Israel and the way the leadership of Israel leads.
i choose to refer to Laitman because he comes out and says it, that criticism of Israel is the same as hating Jews. It's kind of like he says that Jews who don't live in Israel are experiencing Stockholm syndrome.
I see things very differently. I see Laitman and the many right wing, Trump and Netanyahu supporting Jews as being the real Jewish Antisemites. There are a number of different varieties. There are the ultra-orthodox who don't see less intensely religious Jews as being real jews at all. I assure you, they will, with one face, say they support all Jews, but with another, and I've seen that face, suggest that reform or conservative Jews who do not obey the 600+ rules Orthodox Jews follow on a regular basis. Those include reading the Torah regularly, following strict Sabbath rules, men not touching women... not even a handshake.
About 20% of Jews, most of them ultra-orthodox and Orthodox, vote Republican (update: Ironically, these appear to be the Jews most often targeted by recent anti-semitic attacks, which I believe have been inspired by Trump and his White Supremacy supporters.) Some of them are vicious, using the accusation of anti-Semitism to attack progressive candidates with the integrity to take a stand on Israel and not cave to the pressure of AIPAC to give Israel a pass.
That's what's going to happen to Bernie Sanders. Actually, it's already begun. They will go with the playbook that was used to dishonestly accuse UK Labor leader Jeremy Corbyn of anti-Semitism. it worked very well with Corbyn.
These right wing Jews, but attacking the first Jewish candidate for president who has had a real chance in many years, are really attacking Jewish progressives-- and there are millions of them. I say that makes them anti-semitic. I say that when a Jews falsely accuses someone of anti-Semitism, it dilutes the meaning of the accusation of anti-Semitism, just as the boy who cried wolf diluted the meaning of crying wolf.
Noah Berlatsky writes, in his article, for NBC, Is Bernie Sanders anti-Semitic? Why new right-wing smears are the real anti-Semitism,
"The political right has for some time been using charges of anti-Semitism to slander, target and delegitimize left-wing politicians and voters. Support for Palestinian rights, or opposition to any part of maximalist right-wing Israeli government policy can and has been painted as being equivalent to hatred of Jewish people."
"Emboldened by its success weaponizing such charges of anti-Semitism, the right appears to be contemplating using this tactic against an unlikely target - Jewish progressive senator and Democratic presidential primary contestant Bernie Sanders. These attacks both perpetuate bigoted tropes and make it harder to root out real anti-Semitism on the left."
Berlatsky notes that Lowe boasts of her Balkan Chetnik roots, even though they were Nazi collaborators.
Worse, Berlatsky observes that "the anti-Semitic smears are themselves often based in anti-Semitic assumptions and reinforce anti-Semitic tropes, pointing out that
"Lowe's article qualifies Sanders' Judaism, saying that he is merely "ethnically Jewish." This is a way to imply Jewish people who aren't religious are not quite authentically Jewish."
"This ties into general anti-Semitic stereotypes that paint Jewish people as fake or inauthentic. It's the same idea behind the old Stalinist slur that Jews in the diaspora are "rootless cosmopolitans" without any connection to true folk traditions or nationality. In America, conservatives are using it to try to delegitimize Jewish Democrats, who are supposedly "disloyal to Israel," as Trump claimed."
He observes that the biggest group of Israel supporters are Evangelicals who see Israel as playing a key role in "the Rapture." I've written at length on this in my article, The Twilight Zone Metaphor for Evangelicals' Jerusalem Fantasy