Frum combines two talking points:
There is only one last non-military stop on this train: President Obama’s initiative to organize so-called “crippling” sanctions against Iran.
These sanctions would penalize the firms that sell, carry and finance the half-million tons of gasoline that Iran must import every month. (Incredibly, this huge oil exporter and aspiring nuclear power refines only about half the gas it needs.) Such firms are vulnerable to international pressure: Two of the three Swiss firms that provide the bulk of Iran’s gasoline have substantial investments in Canada, for example. If Canada joins the sanctions regime, Canada can bring great pressure to bear on these suppliers and thus upon Iran.
To sustain sanctions over any length of time, however, will require international co-operation, especially from Russia, China and India. Will that co-operation be forthcoming? So far, the record is not promising. But if those countries understand that the final destination of the Iranian effort is an Israeli military strike on Iran, maybe they will rethink. For that reason, the whole world has an interest in enhancing the credibility of Israeli action. For that reason, the campaign to penalize and demonize Israel for its actions in Lebanon and Gaza is an affront to world peace. Only an effective Israel can believably threaten the strike that will incentivize Iran’s trading partners to join the U.S. economic campaign.
So we have gone from denying outright any moral problems associated with the Gaza attack to arguing that, regardless of what actually happened, the whole world should back Israel because of the danger of Iran and the fact that Israel's threatened military strike is the only real lever we have.
Well: let's see how China might view this. They might ask: why should we care if Iran goes nuclear? Or rather: do we care enough that we are prepared to initiate a global terror war with utterly unforeseen consequences rather than tolerate a nuclear - or a latent nuclear - Iran? I think the Chinese would understandably say: nope. Ditto the Russians. They're happy to watch America squirm because of Israel's insistence on either crippling sanctions or war (with no concessions, of course, with respect to the Palestinians).
Would China and Russia move in quickly to fill the gap created by US-European sanctions? You betcha.
Would the Arab and Muslim world blame Russia and China if Israel, with US cover, then attacked Iran? Surely not. The war between Islam and the West after a US-Israel attack on Iran would become as intense as that between Islam and Israel. Russia and China could sit back and watch the American empire be destroyed by a global terror war that simultaneously sends the US economy - and possibly the American constitution - into the toilet. China would suffer collateral economic damage from global depression, but that's a small price to pay to watch the US hegemon go down the drain of religious global conflict.
And let's see how the Iranian people, including the Green Movement, would see this: they oppose sanctions and they oppose military strikes. If the US were to back Israel in crippling sanctions, they'd be accused of being in league with a Zionist plot to starve their fellow citizens. If the US were to tolerate a military attack by Israel, the Green opposition would perforce back the coup regime against a foreign military attack. And every single Muslim and Arab suspicion that Israel controls US foreign policy would be given a propaganda victory.
Tehran's coup regime is wicked but not stupid. They know that on the nuclear issue, they have the winning hand. And if Israel insists on making the US go to the brink over this issue - then the US will lose. Israel may gain a temporary pause before it too faces its end-game. But it's the US that would truly lose.