I don't see where the author makes "broad judgement of all society." I see an opinion piece, which explicitly calls out in the text it's opinionness ("that's how I've come to feel about the Internet") in which the author claims that the Internet "creates terrorists."
This is not an argument that needs statistics or data to back it up - if the Internet creates even one terrorist, then the author's statements hold. The author provides not one, but several examples to support the claim.
It's like you are refuting the headline only, or some adversarial interpretation of the article.
as if there were no other, much older, much more efficient, way to become a killer. Such as : education (think about special forces training), brainwashing (think about suicide attacks), political activism (think about political terrorism in the 60's/70's in europe), etc.
problem with that kind of articles is that it makes it more acceptable to track everything on the web.
All the methods you have mentioned, are, to some extent in the public eye. Imagine the uproar if anti-semitic articles occured in any of the daily news papers. It is a matter of public record, even if some of the methods come out later. Now imagine how many such articles are published and propagandized in online media, away from the gaze of critics, away from serious action by concerned authorities. The power is in the hands of big data companies and they are driven by greed and stock market performance.
Once the papers die, people will start dying too.
Analogy: People being killed in accidents with horses is not an argument for disregarding traffic deaths. Nor can that fact be used to argue against seat belts or airbags. Only if someone were proposing to go back to horse & carriage would it make sense to reference total effects.
If "the internet" wants to avoid the fate of more regulation, it is most sensible to take its critics' worries serious, and to try to find ways to be a positive force in the world without inviting the sort heavy-handed regulations that will otherwise follow.
As but one example, see spam, or child pornography: in those areas, tech companies, users, and governments found ways to effectively work together mostly without resorting to draconian measures.
For an example of such a process failing, look at the EU's recent "link tax": Because the tech community has been so adamantly opposed to taking journalism's existential fears into account, this rather unwieldy regulation will become law. This could have been avoided if, for example, ad blockers had settled for blocking only dangerous and/or the most annoying ads, an approach that could have easily reduced annoyances by 80%+ while costing publishers far less. Or micropayments that actually work, and users to use them. Etc.
Because of its absurdity, that interpretation of the headline can't be correct. So instead of cheap shots (without evidence) about the NYT, you should maybe try to find a valid interpretation, of which there are several. Personally, I'd focus on the "Us". In this reading, it laments the metaphorical death of community, and society's disintegration into autistic strangers.
Like your racist uncle, before people just heard him rant at the thanksgiving table but now the whole world can read his rants on Facebook. The racism was always there, it is just harder to ignore today.
So I'd like to see proof that the Internet actually helps radicalize people. It is true that it makes it easier to find radical groups, but it also makes it easier to find other views which would hinder radicalization. Before if you made a few radical friends they could easily become your whole world! So my naive assumption is that both forces roughly cancels each other out making an open Internet mostly neutral in terms of radicalization.
A hundred years ago, anarchists were shooting people from Milwaukee to St Petersburg. Marxism-Leninism literally took over multiple countries. As long as you have global movement and communications, you have global spread of ideology, you don't need the Internet.
As long as you have cows you will have hamburgers, indeed! But the availability of cheese can nonetheless change the frequency of hamburger, as well as their individual qualities.
By using the internet for radicalisations (a fact almost universal along recent attackers in the US) these people have quite clearly demonstrated their believe in the effectiveness of the net for their cause.
We usually rely on local, individual decision-making to optimise everything, and I don't see a reason why these people (despite their obvious moral failures) should be an exception from this dramatically successful concept. This evidence becomes even stronger considering we're looking at the subset of "successful" attackers.
It also feels intuitively correct to consider the net a tool that helps such movement. That's just because by default, it seems to help almost every endeavour in some way or other. Radicalising a young white nationalist isn't much different from getting them to vote or buy a specific brand of sneakers. If anything, the specific challenges of illegal activities of a small, geographically dispersed set of loners seem to be a unique fit to this particular tool.
https://abcnews.go.com/US/story?id=95379&page=1
It is possible that the Internet has increased politically motivated killings, but articles making broad judgement on all of society based on a couple of anecdotes without proper data is just sensationalist nonsense.