What business do we have in Iran? What business do we have telling any country how it should be run?
As far as the mullahs, read back through history. The US orchestrated the overthrow of the democratically elected president of Iran in 1953 and helped install the right wing, authoritarian Shah of Iran. It was the Iranian Revolution which then overthrew the Shah in 1979. The US presence was ejected because of US support for the Shah.
Just like we helped install the Taliban, Pinochet and Saddam Hussein.