Don't spoil my attempt to be argumentative by agreeing with me!
I was partly thinking of this widely-reported study
https://www.nature.com/news/over-half-of-psychology-studies-fail-reproducibility-test-1.18248
Though it fitted perfectly with my existing perceptions of the field. I've read many descriptions of such experiments that didn't sound very convincing to me. And some of the most famous ones (like that Stanford prison experiment) have been endlessly argued over and seem to have been misreported in the first place.
I also am suspicious that a general disparaging of 'groups' as opposed to 'individuals' might be about pushing a libertarian agenda.
In this case this wasn't really an organised 'group'. If you are going to define some kids who hang out together as a 'group' then surely we are all in groups and there's no such thing as an individual? (Actually, yeah, we _are_ all in groups, nobody could survive as a complete hermit from birth, so it's a bit of a false dichotomy). These youths were products of their upbringing and the society they live in, though just possibly the most relevant thing about them is their age - with a poor start they hadn't had time to gain a bit of decency and sense before being put to the test.
But of course there might have been some of them who were more dominant personalities than the others, and the others just went along with them, but I don't think that's a particularly deep observation.
And you do hear of things like this all the time. The 16 year-old kid allegedly carrying out repeated acid-attacks in London recently maiming people for life just in order to steal from them, the idiot youths who run off to join ISIS..or the wealthy establishment guys who pull amoral-but-legal tricks to leave their workers without pensions. Unfortunately the world has plenty of poorly-socialised people, because human society has a lot of problems.
Thanks, the article in Nature, has made a VERY interesting and informative read for me. It comes as little surprise, because some subject areas, such as Maths, can be readily proved or disproved, in most cases (with statistics, being one of the partial exceptions, as regards actual experimental statistical interpretations, not theoretical statistics). But Psychology, is much more subjective, much less reproducible and much harder to prove etc.
I would say that those 5 boys, were acting somewhat like a group (herd). But we could not see them, and the video was relatively short, and only had the one incident in it. So you still could be right, and they may have been partially (or even fully), still acting as individuals.
One of the voices, did kind of seem to be in charge, and some of the other voices, were sort of speaking back to sort of leader, of the group. But again, this is subjective, and based on very flimsy evidence (i.e. as I already stated, we can't see them and it is of short duration).
Some of the examples you give (although terribly sad, such as the one boy throwing acid at 5 people, over a relatively short space of time), were completely crazy. BUT, if it is ONLY one individual, mainly/solely doing the attacks. Then it can be just one psychopathic/sociopath/crazy/Idiot/criminal doing it. Then it does NOT necessarily reflect badly on society as a whole.
Because there have been murderers and mass murderers, in just about all countries, and at just about all times, in known history, over thousands of years.
E.g. The (ignoring terrorist activities) "idiot/crazies", who go into (sometimes cinemas etc), and perform crazy mass shootings, from time to time in the US. But in all fairness in other countries as well.