Just because the outcome of the research is potentially valuable doesn't mean it's ethical to conduct it on people, especially without their consent.
They explicitly created a situation to depress people, which could definitely increase the likelihood of suicide, particularly if they happened to randomly select someone who already was predisposed to that for other reasons.
I would argue someone at Facebook should've been brought up on criminal charges for this "experiment".
I'm assuming you mean in aggregate?
> They chose to expose some people to predominantly sad and depressing posts, which is not "what they're already being exposed to"
Can you source your "predominantly" here?
If their algorithm is operating randomly, it stands to reason that some amount of people will get a "predominantly" negative feed from time to time. So in this sense, some people were unwittingly being exposed to a predominately negative feed. So it seems reasonable to understand the results of this.
If their experiment resulted in people seeing negativity far beyond what is a possible outcome from their algorithm, then you might have a point about it being unethical.
What criminal law did they violate? Or are you saying there should have been a law against what they did?
I'm aware of only one case where someone was convicted of such a crime in the US without being physically involved in the death: Michelle Carter, who directly and repeatedly encouraged her boyfriend to kill himself, and goaded him into continuing what was ultimately a successful suicide attempt when he started to back out. Despite her active encouragement and unambiguous intent, the legal theory was controversial and the case has seen multiple appeals.
I find it quite unlikely that a court will accept the argument that intentionally making someone sad is the proximate cause of their death by suicide, even if done to a large number of people at the same time. Were that argument accepted, it could be applied to other situations affecting the emotions of many people just as easily, such as producing a sad song or movie.
Knowing this is possible and how to measure the effect, lets them detect when they accidentally do it and reverse course.
Making it illegal to figure out the negative impacts of your decisions will make it harder to avoid them.
It would be much better to require disclosure when these negative impacts are detected and require that this information can only ever be used in the best interest of the user.