In a speech given the day after the death of Abu Bakr al-Baghdadi—the “caliph” of Islamic State (IS)—President Trump stated that Iran had been “right there” in fighting the Sunni terrorist group, along with its allies Syria and Russia. The comment echoed a common refrain of the Obama administration; in fact, the former president proposed in his 2014 letter to Supreme Leader Ayatollah Ali Khamenei that Washington and Tehran join forces against IS, their common enemy. While Iranian troops and proxy militias did occasionally fight IS, writes Tzvi Kahn, partnering with Iran would have been the equivalent of “hiring the arsonist to put out the fire.”

Iran’s efforts to achieve hegemony in the Middle East have entailed the brutal suppression of Sunni Arab populations. In Syria, the relentless atrocities of the Assad regime reflected those of IS itself. In Iraq, a pro-Tehran government marginalized Sunni Arabs and persecuted their leaders. So long as Iran’s expansionist policies remain unchecked, terrorists like Baghdadi will exploit the Sunni-Shiite conflicts that Tehran specializes in fueling.

It didn’t have to be this way. After the fall of Saddam Hussein in 2003, Iran-backed Shiite forces began to infiltrate and co-opt the new [Iraqi] government, enabling Tehran to exert substantial influence in Baghdad. In response to the massacres of Shiites by Sunni insurgents, [Iran-backed] Shiite militias unleashed death squads of their own and planted roadside bombs that killed hundreds of U.S. soldiers. Fortunately, the surge of U.S. forces in 2007, coupled with a new counterinsurgency strategy, gave Iraq a second chance to overcome its divisions. But the Obama administration’s hasty withdrawal of troops in 2011 reversed this progress, resulting in another downward spiral of sectarianism.

The U.S. completed its exit from Iraq only months after the onset of Syria’s civil war, which not only created another haven exploited by IS but also spurred Iran’s military intervention to save the Assad regime. Iran opposed IS in Syria but was more concerned with other rebel groups, both secular and Islamist, that posed a more immediate threat to Assad. Meanwhile, Assad’s brutality—about which Iran had no qualms—led Syria’s Sunni population to cooperate with IS and other extremists as a desperate means of self-preservation. . . .

If President Trump is serious about defeating radical Sunni Islamists who loathe the West as much as they do their regional enemies, then he needs to recognize who America’s friends and enemies are. Islamic State grew out of a sectarian war that Tehran has backed. If Washington fails to check Iran, Sunni jihadism is likely to endure.

Two extraordinary events demonstrate something important about Israel’s most fervent adversaries. One was a speech given at something called The People’s Forum (funded generously by Goldman Sachs), which stated, “When the state of Israel is finally destroyed and erased from history, that will be the single most important blow we can give to destroying capitalism and imperialism.”

The suggestion that this tiny state is the linchpin of a global, centuries-old phenomenon like capitalism goes well beyond anything resembling rational criticism. Even if Israel were guilty of genocide, apartheid, and oppression—which of course it is not—it would not follow that its destruction would help end capitalism or imperialism.

The other was an anti-Israel protest that took place in front of New York City’s Memorial Sloan Kettering Cancer Center, deemed “complicit” in Israel’s evils. At organizers’ urging, participants shouted their slogans at kids in the cancer ward, who were watching from the windows. Given Hamas’s indifference toward the lives of Gazan children, such callousness toward non-Palestinian children from Hamas’s Western allies shouldn’t be surprising. The protest—like the abovementioned speech—deliberately conveyed the message that Israel is the ultimate evil and its destruction the ultimate good, cancer patients be damned.

The fact that Israel’s adversaries are almost comically perverse does not mean that they can be dismissed. If its allies fail to understand the obsessive and irrational hatred that it faces, they cannot effectively help it defend itself.