The rabbi could not find words to answer, and his silence reverberates still. It made clear that an argument that does not embrace a double standard is difficult to come by.

Right-wing politicians and commentators in the United States have been putting pressure on this double standard for years. In her 2015 book, “Adios, America,” the commentator Ann Coulter wrote:

Palestinians demand a right to return to their pre-1967 homes, but Israel says, quite correctly, that changing Israel’s ethnicity would change the idea of Israel. Well, changing America’s ethnicity changes the idea of America, too. Show me in a straight line why we can’t do what Israel does. Is Israel special? For some of us, America is special, too.

Coulter gets her dates mixed up. Palestinians in fact do not demand a “right of return” to their pre-1967 homes, but to their pre-1948 homes. In other words, the issue isn’t the occupation, which many liberal Zionists agree is a crime, but Zionism itself. Opposition to the Palestinians’ “right of return” is a matter of consensus among left and right Zionists because also liberal Zionists insist that Israel has the right to ensure that Jews constitute the ethnic majority in their country. That’s the reason for which Rabbi Rosenberg could not answer Spencer. But if you reject Zionism because you reject the double standard, organizations such as the American Israel Public Affairs Committee or the Jewish Federations of North America would denounce you as anti-Semitic.

It is important to emphasize that in some crucial respects, the comparison between the alt-right’s white-Christian ethnic politics and the Jewish State is not just misleading, but sinister. The history of the Jews — a tiny minority that has faced persecutions, pogroms and the Holocaust — isn’t analogous to that of white Christians. This is an important qualification, and the reason for which, when Richard Spencer speaks of the alt-right as “a sort of white Zionism,” he is promoting a despicable lie. It must be possible to sympathize with Israel and show understanding of Zionism’s historical conditions but to refuse any sympathies to the alt-right. Unfortunately, anti-Zionist critics sometimes fail to be sensitive to this distinction.

But despite sympathy and solidarity with Israel — or better, because of it — any Jew who remains committed to liberalism must insist that nothing in Jewish history can allow the Jews to violate the rights of other ethnic and religious minorities, and that nothing in our history suggests that it would be wise for us to do so.

This is all the more true because by denying liberal principles, Zionism immediately becomes continuous with — rather than contradictory to — the anti-Semitic politics of the sort promoted by the alt-right. The idea that Israel is the Jews’ own ethnic state implies that Jews living outside of it — say, in America or in Europe — enjoy a merely diasporic existence. That is another way of saying that they inhabit a country that is not genuinely their own. Given this logic, it is natural for Zionist and anti-Semitic politicians to find common ideas and interests. Every American who has been on a Birthright Israel tour should know that left-leaning Israelis can agree with America’s alt-right that, ideally, ”Jews should live in their own country.”

Since this continuity is so natural, it has a long and significant history. Last April, Heinz-Christian Strache, leader of Austria’s far-right Freedom Party, was embraced in Israel by top members of Benjamin Netanyahu’s coalition. Strache’s party now celebrates mostly anti-Islam and anti-immigration policies, but it was originally founded by former Austrian Nazis. Jörg Haider, a previous leader of the party, was infamous for showing sympathy for some of Hitler’s policies. Another case in point is Geert Wilders, the xenophobic far-right Dutch politician. This month, it was revealed that Wilders’s visits to Israel and his meetings with Israeli personnel have been so frequent that the Dutch intelligence community investigated his “ties to Israel and their possible influence on his loyalty.”

This phenomenon has been somewhat familiar also in the United States given the close ties between fundamentalist evangelical Christians — whose views on the Jews’ part in a larger messianic scheme is flatly anti-Semitic — and the state of Israel. But with Trump, this type of collaboration is introduced to the heart of American politics.