There is no reasonable way to implement this as a law; is the argument against it.
Either everyone gets tracked by the government openly (which also means your browsing history can be accessed by a foia) or private companies get access to personal information they shouldn't have.
Neither case prevents all access points of porn, but both would require fundamental changes to society itself, as well as internet infrastructure, and would forever isolate any and all states that are stupid enough to implement these requirements.
So yes, kids shouldn't have access to porn. Parents and people in those kids lives are responsible for that, not big daddy government.
If we learn nothing else from the fall of the US we can learn that you do not willingly give the government more power or information.
Nobody has ever been forced to live. Its a choice you make.
That nonsense argument aside, the digital world objectively cannot be legislated like the physical world. Otherwise I'd have stolen more money than has ever been printed or designated. It doesn't make sense to treat digital objects like physical ones, mainly because they share nothing in common.
Pretending like the government needs to know what you jack off to, or pretending that some random megacorp needs a photo of you or your is to keep kids safe is ridiculous on so many levels.
This isnt about buying alcohol, this is about giving the government warrantless access to all of your information for enjoying your own sexuality.