The reasons for failure in all the approaches share a common thread: Iran shrank from any broad bilateral thaw because it feared engagement with the United States more than it feared confrontation.In other words, according to Singh, the U.S. has any number of allies who are able to reach out to Iran, but that Iran is going to reflexively reject engagement with the United States. Singh complains that the present round of sanctions are not likely to accomplish more than we've already seen. He complains that Iran's compliance with Israeli and U.S. "red lines" on its nuclear program allow it to control when those nations might launch a military attack.
“Resistance” to the West — and especially to the United States — was a founding principle of Iran’s Islamic regime. And while Iran has gradually normalized relations with many European and Asian allies of Washington, it has not done so with the United States itself, just as it has not with America’s ally Israel. To lose those two nations as enemies would be to undermine one of the regime’s ideological raisons d’être.
He concludes that the U.S. should negotiate a new track of negotiations with Iran, outside of the current multilateral talks, to address all of the issues with Iran that trouble the United States. He also proposes that we arm-twist our allies to toughen their sanctions on Iran, never mind what that might mean for the progress or outcome of current talks, while telling Iran that they'll support any military action the U.S. chooses to take, while supporting Iranian dissident groups. I suspect that Singh hopes that such a move would cause Iran to walk away from the bargaining table. While pretending to be concerned that "whoever is on the Iranian side actually comes ready to bargain" his actual concern appears to be that Iran will reach an agreement - one of the type he describes as "a narrow technical accord rather than a more fundamental reorientation".
In short, Singh appears to be arguing that the U.S. should pressure the states presently negotiating with Iran to increase sanctions in a manner that is likely to poison any progress. Despite expressing that any such move would trigger reflexive Iranian opposition, he proposes that the U.S. submit to Iran a list of grievances that it wants addressed through separate talks, a move that is likely to undermine the multilateral talks (because Singh clearly wants the U.S. to insist upon concessions that he does not believe will result from a negotiated agreement) while demanding concessions far beyond what anybody (including, and perhaps especially, Singh) believes Iran would find acceptable even if not demanded by the United States. He appears to hope that the U.S. demand will be a new "red line" for military action, or that the collapse of negotiations likely to result from new demands, new sanctions, and new threats would leave the U.S. with "no choice" but to attack Iran.
The question of how to handle states such as Iran, North Korea, and Pakistan, nations that have significant military power and nuclear technology and are hostile to the United States, is not one that lends itself to easy answers. I may be reading too much of a subtext into Singh's argument. Perhaps he truly believes that a nation he paints as likely to reflexively reject any such effort will suddenly become pliant and cooperative if we thump our chest hard enough and make enough threats. But to me, it seems like Singh hopes to create a context in which the United States paints itself into a corner, either having to look like Iran called its bluff or go to war, and that he's hoping for war. Singh might argue that there's a chance that his approach would work - that unlike every other regime in recent history that has faced a similar set of threats and despite his own characterization of its leadership, Iran will capitulate. But it's a "Wish in one hand, crap in the other" scenario - the odds of Iranian capitulation are vanishingly small, such that Singh's proposal is best regarded as a sure path to war.