Earlier quoted context omitted.
Well fair enough. In that case we are actually in agreement. Let the end user (or network admin) sort out what is and isn't acceptable in a given context. What we need regulation to provide (IMO) is a reliable way of doing that.
We don't need regulation, we need cooperation, analogous to movie ratings. A site could attest that they provide content ratings, and that attestation signed by an authority (MPAA). If they are found to have been dishonest about that, the signature is revoked (or probably easier, it's fairly short-lived and just won't be renewed). Browser makers (theatres) cooperate by only loading sites with a valid, signed attestat…
A solution would be browsers refusing to load any site that didn't provide such metadata, not just in child mode but in any mode. I suppose either Apple or Google would likely be capable of unilaterally imposing such a requirement as things currently stand. However I also think that's unlikely to happen on its own for various reasons. Thus legally mandating certain basic content classification categories in addition to an extensible standard protocol for communicating such metadata would (I expect) end the cycle. And rather than the government going after individuals the legislation could be structured to place the onus on mainstream browsers, OSes, and other client software to enforce compliance on their behalf.