The MEK which Mariam Rajavi heads is run like a personality Cult with worship of her and her husband an obligation, so not the nicest of people and Marxist in their political beliefs. However, please also note:
They were labelled a "terrorist group" by Bill Clinton in an effort to appease the Islamic Regime in Iran by offering them this sign of the "USA not supporting your enemies" and even going so far as to set them up as terrorists.
2. France's attack on them - the MEK is headquartered in France (which also gave safe haven shelter and protection to Khomeini before the Shah was toppled) was similar to Clinton's intent and the worry of civil unrest by Mullah inspired Moslems (several million of them in France), so again had nothing to do with anything other than appeasing the Mullahs.
A group so devoted as to self-immolate for the cult leaders, would equally make terric suicide bombers, dying explosively without hesitation while giving some senior Mullah a final hug.
You cannot conduct surgery without a scalpel or a destructive laser beam and many effective medications are actually poisons. With the MEK fervently hating the Mullahs who executed some 30,000 of them, what better tool to excise the Mullah cancer from Iranian society?
Then the "good" people can come in safely with democracy and not be destroyed by the current Islamic terror squads. The MEK have little chance of surviving in power for any extended period of time after they "sandblast" the scene clean for others to step in.