Here she advances a theory that I haven't heard before to explain why ISIS and Iran have such similar views on the execution of law. It's a little surprising that they should -- the Sunni/Shi'a split was more than a thousand years ago, and their schools of law have developed along different lines since then, with the Sunni schools 'closing' the law to reform after the 10th century, and the Shi'a schools remaining 'open' to new interpretations. They are different enough that in Afghanistan, whose constitution says that nothing shall counter sha'riah law, the Shi'a Muslims had to have constitutional provisions protecting their right to practices that Sunni schools of sha'riah do not permit.
Her suggestion is that the reason that ISIS's brutality looks so much like Iran's brutality is that Iran is the real model for ISIS:
Ever since Ruhollah Khomeini came to power in 1979, Tehran championed itself as a successful model, which fundamentalists could follow in order to gain stature, power, and sovereign legitimacy. This presents a tantalizing message to Sunni extremists like the Islamic State– why can they not create their own “Islamic” State when Shiite fundamentalists have already done so?
While the conceptual origins of this extremist ideology took shape in the early years of Islam, it only turned into a formidable global force when fundamentalism gripped Iran in the aftermath of the 1979 revolution.
The regime that replaced the Shah—who was also detestable and undemocratic—began exporting Islamic fundamentalism on an unprecedented scale almost overnight. High-profile hostage-takings, bombings, suicide attacks, and assassinations became the norm as the mullahs in Tehran began building their own version of a theocratic state.
In these early stages, Shiite terrorist factions, including militias in Iraq, Hezbollah in Lebanon, the Houthis in Yemen, and others were directly formed by the Iranian regime. Without such state sponsorship from Tehran, their clout and influence would have quickly evaporated and they would have vanished. The vicious ideology and proliferative model grew increasingly lethal as its proponents gained access to veritable troves of military, diplomatic, political, and propaganda resources within the sovereign state borders of Iran.
So began the first modern-day “caliphate”—years before al-Qaida’s first attack burned in Yemen, and a full three decades prior to the rise of the Islamic State.
Many assume that Sunni fundamentalism is a unique phenomenon, entirely separate from the dogmas espoused by the Shiite mullahs in Tehran, but the differences are ancillary. In fact, Sunni fundamentalists have found tremendous strength under the political and spiritual umbrella of the Iranian theocracy. Both share the same ideological building blocks: the establishment of a religious state, which implements Sharia by force.
There is considerable evidence that the regime in Tehran has armed and financed Sunni extremists at various times and locations. Not only is Iran a long-standing sponsor of Hamas, but also as U.S. Secretary of State John Kerry said recently, “ISIS was created by Assad releasing 1,500 prisoners from jail, and Maliki releasing 1,000 people in Iraq who were put together as a force of terror.” Tehran is the known puppet-master of both.