Question one: How does a duck walk?

When does criticism of Israel turn into anti-Semitism? I’m tempted to quote Justice Potter Stewart on pornography: I know it when I see it.

But anti-Semitism is too serious a charge to level without defining your terms and assembling your evidence precisely. Unsubstantiated charges of anti-Semitism end up backfiring, as the original target dons the mantle of victim and complains he or she is being bullied into silence by the pro-Israel lobby.

That was pretty much the dynamic last week when Tablet — a terrific on-line magazine of Jewish culture and politics — published an ill-advised piece by Hudson Institute fellow Lee Smith on the “mainstreaming” of anti-Semitism.

Smith focused on a number of bloggers for credentialed sites who regularly complain about Israel’s moral failings, America’s support for the Jewish state, and the pernicious influence of the pro-Israel lobby. Included on Smith’s hit list were Philip Weiss (The Nation Institute), Glenn Greenwald (Salon), Andrew Sullivan (The Atlantic), and Stephen Walt (ForeignPolicy.com/The Washington Post Company).

Smith accused the bloggers of “Jew-baiting,” adding that they are “obsessed with Israel and the machinations of the U.S. Israel lobby.” Their blogs inspire posts that turn their websites into an “open sewer of hate.”

Unfortunately, Smith’s essay raises more questions than it tries to answer — the main one being this: Are bloggers responsible for the hateful comments left by readers? Believe me, you can post “Hatikvah” and you’re still going to attract anti-Semites.

The bigger problem is that Smith doesn’t nail down how being “obsessed with Israel and the machinations of the U.S. Israel lobby” is anti-Semitism by another name. The argument can be made — Leon Wieseltier of The New Republic tried to make the case against Sullivan, and Ron Kampeas of JTA has been more successful in demonstrating where Walt and Weiss cross the line. Smith assumes that because someone like Greenwald takes strong issue with AIPAC and U.S. Israel policy the reader will agree he’s a “Jew-baiter.”

Sure enough, Smith’s essay was a slow pitch for its targets. Sullivan responded that he “will not be intimidated from examining and criticizing both the actions of the Israeli government and the lobby that does so much to enable it, against what I believe are the long-term interests of the U.S. and the West.”

What we need is a rigorous lens through which to read criticism of Israel, in order to determine when harsh words are merely harsh and when they dip — hell, plunge — into the well of classic anti-Semitic tropes.

Part of Smith’s point, although poorly articulated, was this: The crazies find comfort in some blogs because they so often traffic in themes that confirm the anti-Semite’s world view. To wit:

Jews exert an influence beyond their small numbers

Not necessarily an anti-Semitic assertion — after all, proud Jews make it all the time. It gets nasty — and medieval — when writers suggest this tiny minority is hoodwinking the majority, which would act reasonably if not for whatever combination of money and magic Jews throw at the Israel situation.

Only the power of the pro-Israel lobby explains America’s Mideast policies

Sullivan has gone down this road, recently complaining that America’s “foreign policy is not determined by rational judgment of the national interest but by the sub-rational passions of a small group.” But this “passion” is shared by millions of evangelical Christians, and poll after poll indicates a majority of Americans tend to take Israel’s side in the Mideast conflict. The pro-Israel lobby succeeds in part because its product is attractive: democratic, Western-looking, and — this is key — on America’s side in the war on terror. Americans distrust the Islamic world, for reasons both rational and irrational, and to them Israel represents the reasonable alternative. Sullivan and Walt can argue why this is muddled thinking on the part of Americans. But to suggest Americans only think this way because of “the lobby” is creepily reductive.

Jews can’t be trusted to think reasonably or fairly about the Middle East

Weiss makes this a specialty. He likes to count the number of Jews who report on or from Israel, and implies their reporting is not to be trusted because of their Israel “connections.” This week he published a list of Jewish administration officials by way of complaining that the White House has too many Jews. “The significance of these numbers is the effect on Middle East policy,” he wrote. “And of course, along with that, the absence of Arab-Americans; and the fact that people like Rashid Khalidi, Chas Freeman and Rob Malley (yes, a Jew, but a progressive one) are exiled from this braintrust.”

This charge assumes, of course, that all of “Obama’s Jews” are of one mind on the Middle East (and ignores “the lobby’s” displeasure with Obama’s policies). There is a name for judging a person on the basis of their religion or ethnicity.

The Jewish community is a monolith

Bill Kristol and Leonard Fein; Jennifer Rubin and Debra DeLee — they may look like political adversaries to you and me, but to a certain kind of Israel critic they are all just voices in the “pro-Israel lobby.” When they deign to acknowledge diversity among Jews, it’s usually to heap praise on anti-Zionists and extremists, like those on John Mearsheimer’s list of “righteous Jews.” It’s not enough that you support a Palestinian state and are willing to criticize Israel’s excesses. Unless you back the flotilla or the Arabs’ Right of Return, you’re just another neo-con.

That doesn’t exhaust the list of strategies that all too easily shade into anti-Semitism. I might add an obsession with Israel that eclipses interest in all other global topics, ignoring any evidence or perspective that suggests empathy for Israel’s policies or motivations, or absolving the Palestinians and their supporters of any responsibility for the conflict.

I don’t know if these guys are anti-Semites or not. I just wish they’d drop the themes that make it hard to tell the difference.