> clearly and explicitly designed to take advantage of these psychological mechanisms.
"Explicit manipulation" is a modus operandi of business and politics. At what point it becomes mephistophelian is largely determined by group conventions.
Social media accounts can become for some people an avatar of self-worth. There is even the reputational business model, i.e. linking business profiles. (Let's leave aside for now the question of streaming sex-work and voyeurism.)
But for the vast majority of users (I estimate hundreds of millions of users, on the back of a napkin), social media is not fatal or damaging. People connect, check friends' news and say hello, then disconnect.
> not proven, but plausible
We know that social media has been used in some cases for bullying and cruelty. The evidence has been tried in court. Social media has been a means of communication in these cases, like the anonymous telephone call or the stamped papermail. (The ghoulish Edgar J. Hoover had his vile FBI operation send at least one letter to MLK telling the civil-rights leader to kill himself.)[1]
The worse tendencies of human nature have of course been known to us for some time. Adam Smith wrecked the job prospects of his friend David Hume. On Usenet of yore, there were flame wars: people pursuing a quarrel because someone is wrong on the Internet.[2] Also consider a funny piece by Woody Allen about two stubborn men playing chess by stamped papermail.
Irascibility, stubbornness, cruelty, and schadenfreude joy are failings of character that are usually treated as legal.
Bullying is a problem and is explicitly punishable in some codes of conduct. To cause death is much worse, of course. It is a crime.
Bullying does happen every day, in hallways and buses and roadways and offices, among people of all ages. There are tyrannical bosses, tavern disputes, cruel remarks in sport, and the art and business of gossip. In some cases, we even applaud a great leader despite that fact that he treats people like rubbish. (I think of at least one famous figure in computing and one former elected leader of a large country.)
In short, I would not say in this case that correlation equals causation, but correlation may indicate something disturbing about the collapse of group ethics and social discourse. I find social media deplorable for the tone of people's discourse. I also don't like television or malicious text messages.
By the way, I upvoted your post. Cheers!
[1] https://en.wikipedia.org/wiki/FBI%E2%80%93King_suicide_lette...
[2] https://rationalwiki.org/wiki/Xkcd