The other day the left-wing blogger M.J. Rosenberg sent an e-mail to followers. After being “deeply involved with Israel for 47 years” (which included four years at the American Israel Public Affairs Committee), Rosenberg wrote that he is taking an indefinite break from writing about Israel. “I’d rather not even think about it,” he wrote. “Especially because I have given up any hope about its future.”

Mainstream Jewish leaders, of whom Rosenberg is a particularly harsh critic, probably replied with a relieved “gei gezinteh heit” — go in good health. Rosenberg reviles the Netanyahu government and especially AIPAC, which, he insists, prevents America from using its clout to broker an end to the Israeli-Palestinian conflict.

Rosenberg is a pretty stark example of the kind of left-wing Zionist Shmuel Rosner had in mind in his recent New York Times op-ed, “Israel’s Fair-Weather Fans.” Rosner, an Israeli who writes for the Times and the Jewish Journal of Los Angeles, addresses a spate of pundits — Ezra Klein, Roger Cohen, and Jonathan Chait, specifically — who say they feel distanced from or disillusioned with Israel. While the Gaza war was the immediate cause of their discomfort, all three agree that, in Klein’s words, “the continued growth of the settlements is morally indefensible” and “deeply counterproductive.”

What most rankled Rosner was the implied “threat” of these confessions: that unless Israel adopted policies good liberals could agree with, they’ll wash their hands of the whole affair — including, presumably, defending Israel in the political and policy arena. “Let me be clear: I believe Israel’s relations with Jews around the world are crucially important,” writes Rosner. However, he adds, “I would never expect Israelis to gamble on our security and our lives for the sake of accommodating the political sensitivities of people who live far away.” Ouch.

Rosner suggests that family doesn’t turn its back on family, and that anyone who believes in a sovereign Jewish state has no choice except to support the only one there is.

Despite what some commenters have written, Rosner’s essay isn’t really about the right of Diaspora Jews to criticize Israel. “Of course, not all Israeli policies are smart,” he concedes, “and it’s not imperative that all Jews agree with them.” Most narrowly, it is about the wisdom of criticizing Israeli military policy in the midst of war, More generally, however, I think his piece is about engagement — that if you really cared about Israel, you would continue to engage with her even when you disagree. To do otherwise is to suggest your ties and sympathy weren’t that strong to begin with.

But if you were to read the liberal Zionist laments as descriptive, rather than prescriptive, there’s deep cause for concern that makes it harder – for Rosner and the rest of us who remain engaged with Israel — to simply say “good riddance.” I found Klein’s essay especially unsettling, because he articulates a position I am hearing more often among Jews just outside the activist “bubble.” “I haven’t become less pro-Israel,” he writes. “But I’ve become much more pessimistic about its prospects, and more confused and occasionally horrified by its policies.”

It doesn’t matter if you agree with Klein or not. The question he raises for those of us in the “bubble” is this: What if Klein represents a trend? What if a chasm opens between the policies of the Israeli government and the politics of a sizable segment of the American-Jewish population (as we saw in the last presidential election)? Are we prepared to say “gei gezinteh heit” to this cohort?

Before you answer, remember to weigh the benefits Israel derives from a strong Diaspora, especially when it comes to representing Israel’s interests as voters and contributors to political campaigns. Jews are also disproportionately represented among opinion-makers. Despite what you think of the media’s performance during the war, support for Israel is the default position in most courts of public opinion in the United States (as opposed to, say, in Europe). The role of Jews as opinion-shapers accounts for much of this.

Also remember that American Jewry benefits from an Israel that inspires. Think about the degree to which Jewish communal life “has been built around and upon the accomplishments of Israel and the challenges she faces,” as the American Jewish Committee put it a while back. Or consider the central role Israel plays in what North American Jewish educators like to call “Jewish identity development.”

If young American Jews disengage from Israel in even modest numbers, what will that mean for the vitality of American Jewry?

It’s also worth remembering that the vicious anti-Israel activity around the world makes no distinctions between Jews and Israelis. To the degree that these acts are a response to Israeli policy, is it credible to say that Israel has no responsibility to the security of “people who live far away”?

And it is not as if the liberal critics addressed by Rosner represent a set of radical positions. All support a two-state solution in order to preserve Israel as a secure Jewish democracy. Like Cohen, they forthrightly declare themselves Zionists. As even Jonah Shepp, a guest blogger for the frequent Israel critic Andrew Sullivan, writes:

[T]he point liberal Zionists have been trying to get across for decades now is that the policy of complete disregard for Palestinian rights and grievances that Israel has adopted is, in fact, gambling on the security of Israelis and Jews everywhere by calling the Zionist project’s long-term sustainability into question.

Nor are they one-sided in their criticism, a frequent charge leveled against the Left by the Right. As Chait writes, “I also bitterly attribute the shriveling of the Israeli left to the Palestinian rejectionists who deliberately engineered” the demise of the two-state solution.

One can argue, as Rosner does, that Israelis should expect the “unconditional love of their non-Israeli Jewish kin.” But what if they can’t? Will Israel be okay if deep feelings for Israel are shared by a shrinking, albeit more impassioned minority of American Jews (augmented, of course, by a good number of evangelical Christians)? What if fewer and fewer Jews accepted Israel’s security arguments, especially when it comes to the Palestinians? Pro-Israel activists have never been stronger or better organized. But what if their numbers, and clout, were to shrink?

We are hardly there yet, and perhaps it is only Israel’s “fair-weather fans” who are jumping ship. But before waving goodbye, we might first ask why they are leaving, at what cost, and what if anything can be done to make them stay. That’s also something families do.