There are various theoretical reasons why this might be so. The most obvious is that rightist politics usually base themselves on cultural, racial or religious purity and unity. This makes Jews outsiders by definition. These rightist movements are also generally looking for outsiders to define themselves against and to pivot against. But these theories matter less than history. Why this is so is much less important than a lengthy historical record which demonstrates that it is so.
As a Jew and a Zionist, I would like to think that this aversion to reactionary politics is rooted in the Jewish cultural tradition or religion. I do believe this to a degree. But the presence of Jewish rightist, nationalist movements in Israel points to a different conclusion: that it is not something intrinsic to Jewish culture but rather that it is part of their defining status as outsiders, Jews' status as a minority, always set apart in key if sometimes limited respects from the majority culture. When outsiders are targeted it may start with Muslims or South Asians or Hispanics. But it comes around to Jews, almost as predictably as night follows day.
Some people are confused by the fact that a lot of our contemporary revanchist groups are militantly pro-Israel. This can be an oddity. But in almost every case this is because they see Israel as a kind of anti-Arab Sparta, a kind of junior mascot specializing in killing Arabs and Muslims.
We are of course seeing arguments now about whether this outbreak of anti-Semitic agitation is tied to Donald Trump. I see little point in actually participating in this argument. Republicans and Trump supporters who deny the connection don't really believe what they are saying. It is obvious that they are connected. We've never seen anything like this in decades. Are the KKK and anti-Semitic white nationalist groups really just confused when they say that Trump is the best thing that has happened to their groups in decades? Are we supposed to ignore that the President's top advisor has clear ties to all of these groups and has spent years bringing them to greater prominence?
This is all obvious - obvious enough that there's really no point debating the point. Whether Trump personally has antipathy toward Jews is irrelevant. His movement and his actions enable and encourage hostility toward Jews and the hostility inevitably spills over into violence. It is not yet as lethal. But it is no different in its basic contours to the immigrant bashing that led to the murder of the Indian immigrant Garmin employee in Kansas.
Demonization breeds hate and hate spills over into violence, all as surely as night follows day. There was a new round of bomb threats just this morning.