Online age verification is an example of the Motte-and-bailey fallacy (https://en.wikipedia.org/wiki/Motte-and-bailey_fallacy, https://slatestarcodex.com/2014/11/03/all-in-all-another-bri...).

It is easy to defend on the motte hill (protection of children, protection against abuse and heinous crimes), and easy to expand and farm on the bailey (universal surveillance, mass data collection, and the erosion of privacy).