I knew vaguely about incels thanks to reddit, and I think the article does a reasonable job (or at least is consistent with what I observed and the conventional wisdom on reddit). Before it was banned, /r/incels was a horrific place. And now it's all just on /r/braincels, since reddit doesn't actually give a shit about terrible communities (just the publicity). Braincels also has added Hitler.
To me, it seems like an odd case of pareidolia. Guys have this idea of how they "should" be viz. sexual exploits, but they aren't that (and almost no one actually is). But rather than accept it, or change themselves, some take the easy way out: blame everyone else. And it becomes self-perpetuating: the more into the incel idea someone becomes, the more warning signs they're going to send off to someone else. This just reinforces the idea that women are all shrews or whatever.
My theory is that it's this weird offshoot of, ironically, women's lib. Let me preface by saying that I don't blame feminism, or think that at least some of it shouldn't have happened (which isn't to say they don't have their share of crazies too, i.e. half of tumblr). Anyway, a lot of guys around my age, i.e. born in the early-to-mid '80s, were taught to be much more conscious of how we approach women. On the other hand, popular culture still generally showed us portrayals of men being pursed by women and being shot down. So on the one hand, we're told to be wary or suspicious of our own sexuality, and then on the other, to expect harsh rejection (that this portrayal isn't really accurate isn't the point, since it's perceived to be). Meanwhile, guys who for whatever reason have the courage to pursue someone anyway are more successful. Our proto-incel is left confused: he did everything he was taught, but was unsuccessful, while the guys who do the very things he was told were wrong is able to get dates all the time.
As with anything else, this becomes a crossroads. It can lead to self-reflection and refinement of one's models, as it were. Or it can lead to anger, frustration, and rejection of the whole thing. The latter, it seems to me, likely will often have some cofounders, i.e. people who tend to be less well-adjusted for whatever reason anyway.
Are we as societies, both big and small, really doing our best to combat isolation?
Absolutely not. To an extent, societies are at their core about dividing ourselves into groups. The problem is that it's become so much easier to do, and once you are in a group, you have far less contact with others.
That said, I do wonder to what extent things are in some way "worse" than at a previous point. Groups of terrible people have always been a thing, and I wonder to what extent we're just hearing about them more. After all, murder in the U.S. is at its lowest levels in generations, but at least as of a couple years ago, surveys showed people consistently thought the murder rate was going up. So I think we have to be careful not to conflate "hearing about it" with "it being prevalent," since God knows the media likes an exciting story.
Knowing this, are forums like the ones described in this article an example of free speech and anonymity going to far? Can anything really be done about it while still respecting the rights of individuals?
No to both. Principles aren't principles if we only adhere to them when they're convenient. And we can always rationalize away something that's hard, even if it's ultimately perilous to do so. Today incels, tomorrow socialists. Or whomever.