Republican Jews have no problem criticizing the likes of Stephen Walt, co-author of The Israel Lobby, a book claiming that the pro-Israel lobby holds control over American foreign policy. Walt also argues against the U.S.-Israel relationship.

Walt’s co-author, John Mearsheimer, has endorsed a book by anti-Israel extremist Gilad Atzmon, and the anti-Israel left touts the two co-authors.

The Republican Jewish Coalition also has gone after Chas Freedman, who has said he was “wrong in my presumption that Israel desired peace.”

Republican Jews likely aren’t fond of Barry Posen, who runs the international-relations program at the Massachusetts Institute of Technology, and in his book, Restraint: A New Foundation for U.S. Grand Strategy, pairs Israel and Iraq as “reckless drivers” that “do the wrong things.” Posen urges less military assistance for Israel, and says that that the United States should reduce its “salience” in the Middle East, particularly in the Israeli-Palestinian conflict. He also favors cutting the American defense budget.

Michael Desch, who directs the International Security Center at the University of Notre Dame, has called for Israel to accept the 1967 borders as “the starting point for the two-state solution, that Jerusalem will have to be shared as the capital of both states, and that some provision, however symbolic, will have to be made for the Palestinian refugees of 1948.” Not something that Republican Jews would abide.

Eugene Gholz, a professor who recently moved from University of Texas to Notre Dame, is a regular player at Koch Foundation-sponsored events. He calls for changes and cuts in defense spending, the elimination of regional combatant commands and shifting away from military support for allies. At a Charles Koch Institute Roundtable, Gholz said “it’s true” that Russia is doing “the lord work” in Syria.

What these academics all have in common—aside from their often hostile and at times outright dangerous perspectives on Israel—is that they receive funding from the Koch brothers, whose protectionist and isolationist attitudes have been compared with those of U.S. businessman towards Nazi Germany in the 1930s.

In a recent Tablet exposé,Koch dark money funds anti-Israel darlings,” anti-Israel figures typically associated with the far left are now getting support from the far right as well: “In 2018, isolationist sentiment and anti-Israel conspiracy theories have found homes on both ends of the ideological spectrum.”

Through his foundation, Charles Koch, who has vowed to spend millions of dollars to support Republicans in the upcoming elections, is arming isolationist college professors with money and a platform to push their shared foreign policy agenda. By elevating these professors, who self-identify as “realists,” Koch promotes massive cuts to U.S. defense spending and retreating from American leadership around the world, particularly from the U.S.-Israel relationship.

Many of the academics Koch supports are outspoken critics of the Jewish state, and their policies would give more power to Russia, hurt Israel and end America’s role as a world leader. These “realists” call for cooperation with Russia, ending NATO, and even agreeing that the U.S. should view Russia as an ally and that Russia should take over on the ground in Syria. Russia on the ground empowers Hezbollah, Iran and Syrian President Bashar Assad—all three seek Israel’s destruction.

Walt and Posen direct the Charles Koch Foundation-funded Grand Strategy, Security and Statecraft Fellows Program, a joint Harvard-MIT program.

Since releasing their book, Walt and Mearsheimer have become strongly identified with attacks on the U.S.-Israel relationship. The two have said that the America should distance itself from the peace process: “Repeated U.S. attempts to broker Israeli-Palestinian peace have failed, leaving a two-state solution further away than ever.” In March, Walt sarcastically referred to the “geniuses who dreamed up and sold” the Iraq war, listing by name eight foreign-policy hawks. Of the scores of people he could have listed, seven of those he singled out are Jewish.

Beyond funding academics with worldviews that are largely hostile to Israel, Koch has funded organizations tied to those who deny the Holocaust and to white supremacists, according to unkochmycampus.org. In a report titled “Advancing White Supremacy,” unkochmycampus.org notes, among other things, that the Koch-funded Reason magazine gave voice to Holocaust-deniers and neo-Nazis.

So, here’s the question for our Republican Jewish friends: You’re quick to condemn anyone on the left you see as a danger to Israel, so where’s your condemnation of Koch?

We, supporters of the U.S.-Israel alliance, Democrats and Republicans, need to stand together in that fight, regardless of who’s cutting the check.

Aaron Keyak is a former head of the National Jewish Democratic Council and currently the managing director of Bluelight Strategies, a consulting firm based in Washington, D.C., with many progressive and pro-Israel clients.