One of the most notorious newspapers ever published in America was The Spotlight, founded in 1975 by white supremacist Willis Carto. For many years the country's premier hate rag, it peaked at 330,000 subscribers in the early '80s. Alongside support for South African apartheid and exposes of the Bilderberg group, the paper was a regular purveyor of Holocaust denial, with stories like "Jewish Groups Can't Defend Position on '6 Million' Debate" and "Anne Frank Fable Losing Credibility; Establishment Continues to Push 'Diary' as 'True Story.'"

The Spotlight, which thankfully ceased publication in 2001, wasn't just concerned with falsifying history. When not questioning the existence of the gas chambers, it focused on the "Jewish lobby." And its writers had two terms for describing U.S. Jews and their activism on behalf of the Jewish state: "dual loyalists" who were for "Israel first."

When Zaid Jilani was recently informed that his use of the latter term had anti-Semitic implications, he professed ignorance. Jilani, a blogger at the Center for American Progress (CAP ), claimed to be "unaware of all the connotations it carried." That a young blogger at a prominent liberal think tank would see nothing wrong with such language is understandable. It's an indication of just how deep the rhetoric of the far right has seeped into the discourse of the mainstream left.

Jilani is one of several individuals who have come under fire for their commentary regarding Israel and Jews. The controversy started in early December, when Politico detailed how two "core institutions" of the Democratic Party - CAP, a farm team for the Obama administration, and Media Matters for America, a self-described "progressive research and information center" - "are challenging a bipartisan consensus on Israel."

Rather than addressing the substantive criticism raised, CAP tried desperately to change the subject, turning its guns on those airing concerns, particularly Josh Block, a lifelong Democrat and former American Israel Public Affairs Committee spokesman whose criticism of the groups was quoted in Politico. The episode approached the status of Washington "scandal" when liberal website Salon published a dossier Block had disseminated documenting a series of blog posts, articles, and Twitter messages in which CAP and Media Matters employees batted around rhetoric and accusations as if "it's now just natural to talk about Jewish money in politics, about treasonous politicians."

To judge from Block's collection, the worst perpetrator is Media Matters' "senior foreign policy fellow" M.J. Rosenberg, whose "analysis" largely amounts to name-calling. Newsweek reporter Eli Lake is an "agent of influence." Playwright David Mamet is an "Israel first Likudnik." Indeed, any U.S. Jew to his right (including Democratic congressmen ) is an "Israel-firster." When one journalist complained about Rosenberg's calling her a "dual loyalist," he responded by saying, "I say DUAL which is generous." No wonder he best expresses himself in the Twitter medium of 140 characters.

Block took considerable professional risk in challenging these two influential liberal organizations. The Truman National Security Project, a once-promising initiative to promote a hawkish sensibility in the Democratic Party that has since become little more than another greasy pole for young D.C. opportunists, expelled Block from its fellowship program.

In the Forward, Sarah Wildman attacked Block, writing that "When we debase the term [anti-Semite] by using it as a rhetorical conceit against those with whom we disagree on policy matters, we have sullied our own promises to our grandparents." But it is those who use the term "Israel-firster" who are debasing the debate by accusing anyone who disagrees with them of treasonous impulses. Wildman also argued that the offensive comments had been "taken out of context" - as if there were ever a context, other than that of, say, Jonathan Pollard, in which it would be appropriate to label an American Jew an "Israel-firster" or "dual loyalist."

Ultimately, however, Block was vindicated. While CAP publicly denied that its employees were trafficking in anti-Semitism, an e-mail from the organization's vice president, obtained by The Jerusalem Post, deemed "Israel-firster," to be "terrible, anti-Semitic language."

The left is constantly complaining that the debate about Israel is restricted, that one can't criticize Israel without "risking" his career. Reality is in fact the opposite. Figures ranging from University of Chicago professor John Mearsheimer to journalists Peter Beinart and Andrew Sullivan have all seen their careers blossom as a result of their harsh and unrelenting criticism of Israel. Indeed, obsessively attacking Israel is a bona-fide way to resuscitate one's career, not destroy it. As a measure, consider the fact that employees at mainstream liberal institutions feel comfortable using the sort of language popularized by white supremacists and Holocaust-deniers.

It isn't just figures on the medium and lower rungs of think tanks using such foul rhetoric: "Israel-firster" and "Likudnik" are favorites of Time's Joe Klein, as well as Salon's Glenn Greenwald, one of America's most popular liberal bloggers, who refers to "the many Israel-firsters in the U.S. Congress."

Since the 1950s, liberals have routinely accused conservatives of "McCarthyism." Now the tables have turned, and it is leftists questioning the loyalties of American Jews. Judging what's in a country's "interest" is highly subjective; it is the very reason why there exists such passionate and necessary debate about the purpose and tactics of American foreign policy. So-called "progressives" should stop mimicking the far right and engage in that debate without questioning the allegiance of their fellow Americans.

James Kirchick is a fellow of the Foundation for Defense of Democracies and a contributing editor for The New Republic.