Even though you're filtering out the less-radical and committed members of a population, you're also priming everyone left behind to be more sympathetic to the excesses of the people who stuck around.
These were tolerable outcomes for already fringe communities.
But as the technique is scaled up to impact increasingly broad segments of the population, I believe it creates something increasingly large, and increasingly dangerous dangerous.
That's not a problem, unless you feel society ought to "save" everyone from themselves (as opposed to protecting society at large from bad actors).
I share your sentiments, but the current US prison system tends towards isolating bad actors: no real effort is expended to reduce recedevism, with the goal being punishment rather than rehabilitation.
I think that need to communicate without external interference is at least as strong in people as the need to light up a joint. Even in China, where controls on communication are very strong, people manage to find a way to circumvent the limits. Much more so in other autocratic regimes, such as Iran.
Drug offenders are more likely to become low-level criminals, check out of society, unemployed, or impoverished. They may also be more likely to latch onto fringe groups that offer them an identity or sense of empowerment, but that latching isn't deterministically going towards any particular group.
They're imprisoned for a crime that they likely know is bullshit, but the thing they're imprisoned for is amoral to them, and a personal matter. Smoking weed or doing opiates is not a coherent commentary on the social order. Becoming a drug user is a matter of weighing the risks vs the rewards that come with it in the moment you choose to start. They likely just want to live their lives.
When they are caught and punished, they are locked up, and afforded no freedom of movement whatsoever.
Their punisher is the government, a massive byzantine machine with power which society has collective assumed to be legitimate (anarchists excluded). The enforcers of those laws may be dicks, but they are as much an extension of that somewhat legitimate power as the sympathetic public defender you may be about to receive.
Systematically and repeatedly cutting the communications ties of a massive political block for the behavior of their worst actors has a very different effect.
The locus of their concerns is by its very nature external, they already have a collective conception of who their opposition is, and the people repeatedly cutting them from their social circles are not only unelected, but entirely lacking in political legitimacy despite their massive power. They perceive that what they do is much less an indicator of whether they'll be affected than who they might possibly be with.
I believe that this creates an ample breeding grounds for the next generation of domestic terrorists in a manner that gives them concrete grounds for their sense of isolation, while simultaneously creating an ambient corps of collaborators and sympathetic allies in society at an unprecedented scale.
Parler is by no means a niche application. One of my bosses, a milquetoast Republican who was entirely contemptuous of the Capitol incident, and was talking about regretting his vote for Trump afterwards has it on his phone, because he fancied a Twitter alternative for conservative ideas. He has no conception that he might be a potential domestic terrorist. All he'll perceive is that 'Democrats' in 'big tech' are trying to ban the opposition party now that they've secured all three branches of the government.
To him, violent extremists will increasingly look like freedom fighters, and a mild sense of annoyance at 'progressive tech' will increasingly become an awareness of a perceived institutional threat to his way of life.
The key distinction is between people who seek out certain content and people who stumble across it passively (in a morning car commute, say). The latter can actually be de-radicalized and de-programmed much more easily, and it's a worthwhile task to do so. Trumpism is a cult, and so the deprogramming methods have to be similar to recovery from a cult (and not the typical arguments that we see on facebook and such which are completely useless & worse)
That's the reason for why it was removed, not simply because Apple doesn't like conservatives as they will claim.
The aim isn’t to remove the sites entirely, but to make it difficult enough to find that people won’t just stumble across them or seamlessly follow a link to them.
Last I heard Stormfront still exists on Tor and presumably still serves a dedicated audience. But I imagine it has a considerably larger problem attracting new readers than it used to.