[tech2]

They may not be against content restriction, instead they may be against removal of user privacy or anonymity. If the proof of age thing was some kind of zero knowledge proof such that the age verifying group has no knowledge of what you're accessing, and the site you're accessing has no knowledge of you as an individual (beyond tells like IP address etc.) then perhaps they'd be more open to it?

[AnthonyMouse]

There isn't any technology that can prevent sharing of age verification with third parties without tying your uses to your identity. To unmask someone in order to uncover sharing, you would require the ability to do it in general, which is incompatible with privacy/anonymity.

[subscribed]

And yet homomorphic encryption is a thing. It's possible to process the encrypted request and be unable to see it.

Similarly we could easily devise many solutions that can prove the age in the privacy - respecting ways (like inserting the age-confirming token inside the pack of cigarettes which an adult could then purchase with cash, etc)

Many ways.