US Secretary of State John Kerry may feel heartfelt concern about the growing campaign to delegitimize Israel and to boycott it. One of the least smart and least constructive ways to tackle the danger, however, is by issuing an anguished public prediction that this is what awaits Israel if his peace effort fails.

But then the indefatigable secretary has consistently displayed a grievous absence of smarts when it comes to Israel, and the wider Middle East.

It remains inexplicable how Kerry, on taking office, could decide that he was capable of bridging the gulfs between a weak-willed Palestinian Authority President Mahmoud Abbas and a profoundly skeptical Israeli Prime Minister Benjamin Netanyahu, in an era of utter instability in the Middle East. Did his hubris obliterate the recollection that less than five years earlier, a far more flexible Israeli prime minister, Ehud Olmert, operating at a time when extremists were not filling every possible territorial vacuum in Israel’s immediate neighborhood, was rebuffed by Abbas with a peace offer Netanyahu would never come close to replicating?

Undeterred by two decades of incontrovertible evidence that setting deadlines and trying to turn the screws on the Israeli and Palestinian leaderships to force a deal simply doesn’t work, Kerry publicly professed his confidence not only that he would soar where all predecessors had failed, but that he could achieve the hitherto impossible in a mere nine months.

When reality first bit, he withdrew to nurse his wounds, and returned with a fallback position: A full peace deal? Well, perhaps not. But how about a “framework” covering the big issues, so that we can at least keep talking beyond the unfeasible deadline.

In the last few weeks, though, it has become clear that even a binding framework agreement is beyond reach. No, Mr. Netanyahu does not trust the Palestinian Authority to keep Israel secure from the east. No, Mr. Netanyahu does not believe Abbas’s regime would long survive without the IDF in the area, and is not prepared to risk a Hamas takeover of the West Bank. No, Mr. Netanyahu does not intend to drag tens of thousands of settlers out of their homes. No, Mr. Abbas will not belatedly decide to confront the narrative permeated deep in the Palestinian psyche by Yasser Arafat and suddenly declare that the Jewish state is legitimate. No, Mr. Abbas will not publicly abandon the demand for a “right of return,” even though that demand amounts to a call for the demographic destruction of Israel and therefore prevents the establishment of Palestine.

So the secretary has fallen back again; seeking now to broker a non-binding framework agreement, as a vehicle to keep the talks going. Well, if you set the bar low enough — as the P5+1 countries proved so dismally in Geneva in November — even the most recalcitrant players may be persuaded to clear it.

Kerry’s public musing in Munich at the weekend about Israel’s “illusionary” thinking on peace and prosperity sounded like the moaning of a petulant child: I want my nine-month peace treaty, and I want it now!

(Let me stress that I have no time for those on the rejectionist right who waded in to publicly assail the secretary. The Naftali Bennetts, Ofir Akunises and Danny Danons of this world dismally seize every opportunity to advance their one-state non-solution.)

Israel, Mr. Secretary, has no illusions about the hostility all around it and the anti-Semitism painted as anti-Zionism further afield. It has no illusions, either, about the fragility of its current economic well-being. It has a prime minister who finds it unconscionably hard to defy the extremists who would subvert its democracy by populating remote areas of Judea and Samaria that Israel has no intention of permanently retaining, and who wish to see us ruling over another people for the foreseeable future. But this is a prime minister, too, who has freed 78 largely unreformed terrorists in the cause of these peace talks (unfortunately so; he should, rather, have instituted a settlement freeze), who has publicly embraced the two-state solution, who is plainly prepared to contemplate territorial compromise even with the region in such dangerous flux.

The true path to Israeli-Palestinian peace lies not in attempting to strong-arm reluctant, mistrustful leaders to sign up to this or that latest lawyerly draft of an accord. It runs, rather, via the gradual marginalization of extremists and the encouragement of moderates. It requires ending the vicious incitement against all things Israeli, not just in Gaza but also in the West Bank, and the promotion of hierarchies that advocate reconciliation.

This takes work — gradual, painstaking work, from the sides themselves, helped by the outside would-be peacemakers. That doesn’t mean a dozen more two-day attempts at coercive top-down shuttle diplomacy. It means real engagement, led by the US, involving the wider international community, identifying educators and investors and journalists and every other potential grassroots advocate of reconciliation, gradually achieving change from the bottom up, which in turn will impact leaderships. There is no quick fix. But there are slower fixes. It’s not that we need less outside help; we need more, but properly directed, strategically directed.

Good diplomacy also involves reading the riot act, privately, to Netanyahu — telling him that while Israel will always be portrayed as the key obstacle to peace because it has a state and the underdog Palestinians don’t, the prime minister would help his cause if he seized the initiative as a credible force for moderation by, for instance, announcing that there will be no further investment in isolated settlements and that the residents of those settlements can seek financial compensation at any time to relocate to consensus areas.

And good diplomacy requires telling Mr. Abbas that there will be no Palestinian state so long as he insists upon the “right of return,” because Israel, the only place on earth where the Jews get to determine their own fate, is not about to commit demographic suicide. It requires telling Mr. Abbas to change the tone of what’s taught in his schools, broadcast on his TV channels, and published in his newspapers, to reflect the reality that there are competing claims to this narrow strip of land and that neither of the competing peoples is going anywhere.

Good diplomacy, Mr. Secretary, means that you most certainly should address the boycott and delegimitization issue in public — to make plain that it is unconscionable to misrepresent Israel as some kind of illegal entity; to explain that the notion that the Jewish people, uniquely, has no right to a state is an apartheid argument; to underline that historic Jewish Israel was revived by international mandate and that it was those who spoke for mandatory Palestine’s Arab residents who prevented the simultaneous establishment of a first-ever Palestinian state 66 years ago, and to urge that those who purport to support the Palestinian interest use their influence to encourage both sides toward viable positions that can enable long-term co-existence.

And good diplomacy, centrally, involves taking practical steps to marginalize those outside powers that relentlessly foster extremism and terrorism and violence — those enemies of peaceful co-existence — led by Iran. The Obama administration failed the people of Iran when they tried to rise up against their regime. It has failed to protect the people of Syria from slaughter. It has offered no coherent guidance to would-be democrats in Egypt.

And its latest diplomatic “achievement” has set Iran more firmly than ever on its path to nuclear threshold status — allowed to enrich uranium, allowed to improve its technology for enrichment, allowed to continue its weaponization and missile development programs. The Iranians came to the table desperate, and you, Mr. Secretary, sent them home crowing — failing to use your authority and influence to force their admission that they were working toward the bomb and to ensure they were halted.

In short, the most profound concerns that Israelis have about the fragility of their security and prosperity stem somewhat less from their failures, Mr. Secretary, than from yours.