We can always use more case studies of insanity that aren't religion, right?
Well, Miracle Mineral Supplement is my new go-to example for Bad Things happening to people with low epistemic standards. "MMS" is a supposed cure for everything ranging from the common cold to HIV to cancer. I just saw it recommended in another Facebook thread to someone who was worried about malaria symptoms.
It's industrial-strength bleach. Literally just bleach. Usually drunk, sometimes injected, and yes, it often kills you. It is every bit as bad as it sounds if not worse.
This is beyond Poe's Law. Medieval blood draining via leeches was far more of an excusable error than this, they had far less evidence it was a bad idea. I think if I was trying to guess what was the dumbest alternative medicine on the planet, I still would not have guessed this low. My brain is still not pessimistic enough about human stupidity.
Bleach will control (kill) most bacteria, but since cancer cells are very similar to your own cells, the prior is very low unless there is a specific reason to think that it will target one of those differences. For example, something that is just corrosive will probably affect the different cell types equally. Another thing is that since it's a charged molecule, it can't actually enter the cell on its own unless it rips apart the cell membrane, in which case that's probably the main mechanism of toxicity.
Also, I wouldn't be surprised if it had been tested. The most likely outcome would be that it failed at an early step in the testing process (along with a large number of other chemicals), and nobody had any reason to publish it or think that anyone would ever actually decide that it might work.
All good points, which, incidentally, invalidate the OP's assertion that he is 'still not pessimistic enough about human stupidity".