Just after the revolution in 1979 after Khomeini returned from France, thousands upon thousands were arrested and executed. The Iranians, even his vigilantes, refused to shoot their kinsmen, kinswomen and pre-teen children, so Arafart's 2,000 Palestinians who cane to Iran with him to get money from Khomeini and plunder the artifacts and antiques from the homes of the arrested and executed wealthy, had to do the job. Finally they started threatening the young Iranian vigilantes with death if they did not pull the trigger. After a while the Iranians became inured and handled all the executions - but still rather reluctantly. That was when Khomeini set up the Pasdaran (Revolutonary Guards) as his personal guards and also the mercenary Basiji as enforcers. As I was discussing with a Persian friend, there used to be about half a dozen real (premeditated) murders in Iran every year, other than the occasional manslaughter incidents where someone got killed by accident in an altercation both in a village over crops or in a downtown knife fight. Pre-Khomeini Iranians were not naturally bloodthirsty. The Islamic regime has bred a new kind of Iranian. Rapes and murders began to take place after Afghans who had come to Iran to find work during the Shah's time no onger found work and discovered Khomeini did not much care if they killed, robbed and raped.
In order to maintain totalitarian rule, it is helpful if you have people who are totally alienated from the people whose heads they will need to bust. So, to rule over Shiite Persians, get Sunni Arabs.
The British in India used Muslims to rule over Hindus
In the US, an alarming sign would be if the government undertook major recruiting of people out of the welfare enclaves for federal "law enforcement"