[kevingadd]

The main indications that a line was crossed are the combination of a blatantly questionable hypothesis ('we can make people depressed or unhappy') with an intentional lack of informed consent & a huge set of test subjects.

If you're doing medical testing in order to roll something out as a pharmaceutical for prescription use or over-the-counter sales, the tests are rolled out in stages, with initial testing being done on a very small number of patients under extreme scrutiny, and even that is only done after the medication has been vetted carefully using animal models. It's extremely important to avoid harming your test subjects.

In comparison, they basically went full-steam on this experiment on hundreds of thousands of people despite the fact that emotional manipulation of this sort is EXTREMELY DANGEROUS. When I say extremely dangerous I mean potentially life-threatening.