If a simple flue kills you, it may be the flue was a very great killer - or it may be that your immunity system is very low.
If US mentalities « snap » under « communist brainwashing » (like Prisoners of War, Corea), « sectarian brainwashing » (used, apparently, by doctrines as different from each other and from Communism as: the Moon sect and Hare Krishna, the near-Christian close to Voltarian twins Scientology and Watchtower Society, and not forgetting « adepts » to « extreme varieties » of Catholicism, Islam, monasticism, domesticity, fasting, praying on beads or prayer ropes, et c.) it may be they are all great « mentality killers » or brainwashers - or it may be that US mentalities have some very weak spots (economic justice, in a country where nobility and clergy are traditionnally looked down on as « wealth without work », but great capitalist speculation abounds; illogical compromise on theocracy and anthropocentrism issues; the hypocritical accusation of Amerindian genocide against the Spanish who committed great massacres, but never against entire peoples, when XIXth C. US then did massacre or totally assimilate entire populations, the liberty cult and American dream along with Malthusianism; the Whig History - to name only some).
In fact, Margaret Singer forgot a few of the new mentalities or « sects » into which US mentalities snap. She forgot her own thoroughgoing antireligious lobby. And she forgot the hippie thing.
Indeed, it seems that some of the people she « deprogrammed » from « sectarian brainwashing » might have resented her intrusion into their lives. She did receive weird visits and something like threats the last years. And that is much more a thing some loner whom she had done bad by would do than a sect - always on the watch for their legal status in societies where they are nowhere near a majority - would be apt to organise. Of course, she was also an « expert » on "Schizophrenia", and she might have victimized people even more so in that capacity.