The problem with your source is that it doesn't negate what the OP is saying.
We have countless examples of people acting in a mob mentality manner because of social media. Moral panic in many ways is a type of mob mentality. I'm not exactly sure how an example (your wikipedia link) of people acting in senseless ways because of what everyone else is doing is supposed to negate people acting in senseless ways because of what everyone else is doing.
There is direct evidence of social media influencing bad patterns of behavior, even if you wouldn't consider this an obvious point, there is hard evidence for it. Everything from which hunts, to bullying people, to SWAT'ing, to getting people to shoot up a pizza place.
>but the state tends to do it even worse.
I'm not sure what evidence there is for the state not being able to adequately control socially-negative behaviors (well, besides drug use, but there is an extreme biological motivation for drug use). We often look to the state in times of social crisis or socially tense situations and it's done a pretty damn good job. Saying the "state does it worse" seems like bald-assertion that ignores the countless examples of where the state sufficiently guides social practices. You could very well argue that you don't like the state doing this, but the state is definitely able to consistently influence social behaviors. Everything from the FCC regulating content to the government influencing common sexual practices.
OP seems to be basing his opinions and perspectives in actual experience and with evidence, without resorting to typical "the government can't do that (even though it already does)" talking points. So good on him.
If it wasn't obvious I definitely think we should be regulating on-line content. The modern internet has shown that it's a tool, and it can be used to empower the darker sides of human behaviors. There is absolutely nothing wrong with curtailing that.