This is a problem in open societies like the US and Europe. There a lot of "sects" choosing to wall themselves off, but they are learning to wield considerable political power in doing so.
I think a lot of people are talking about that, and have been for some years. There's certainly a lot of articles to be found about it going back a few years, and many of the intervention and prevention programmes discuss the appeal of jihadi ideology to European youth.
A major problem in Europe is that there is no challenge to jihadi rhetoric, except for the far-right freak show, because the whole thing is taboo. You can't defeat jihadi ideology by pretending it doesn't exist, which is what you're effectively doing when you restrict online access and communication. It's a knee-jerk yet cowardly way to avoid confronting the problem.
To a reasonable person, it should be obvious this is just a proximate cause and not the root cause. Browsing the internet and then being exposed to hateful ideas doesn't automatically turn you into a murderer.
The deeper cause is surely that "jihadi ideology" is effective at appealing to European youth. But nobody is talking about why this is in fact the case or what are the reasons why it is so attractive to some people.
For one thing, the problem of jihadi terrorism isn't going to go away without confronting the ideology head-on. I think we must have a painfully honest discussion about "jihadi ideology" and to debunk it. Radicalization isn't an inevitable outcome of being exposed to these ideas but is rather the result of losing the argument with friends, loved ones, civilization.
Banning this stuff isn't going to make it less appealing to some people or to make it disappear from the internet. But it does give government the power to censor ideas they deem to be dangerous and liable to "brainwash" the youth. And you have to ask whether you trust your politicians to use such powers responsibly.