Hormesis might be relevant here. I don't see a compelling reason to believe these people are not being helped in some cases.

I see no reason to expect hormesis to be relevant. Typically, hormesis is about really low doses, sometimes to the point where accidental contamination is a confound: for example, in radiation hormesis, I've read of measures like using ancient marble or lead as shielding because they will have less residual radiation than other materials. If the bleach hormetic doses are that small, then all they're doing is poisoning themselves by going way beyond hormetic doses...