Their argument seems pretty lame to me. If at least one third of the content is sexually explicit, it's a porn site. Why would requiring age verification be a problem, if it might discourage kids from accessing it? I don't think an adult's right to KYC-free masturbation is more important.
Discussion
And you're ok with some people deciding what is and isn't adult content? I like my internet unfiltered, thanks.
And the worst sites won't even comply. So when kids go looking, they'll find potentially more harmful porn
There are plenty of sites where I don't think it's controversial, although for sure there are grey areas.
I'm almost always opposed to restricting access to anything on the internet, but I think different principles come into play when you're talking about kids. We can't really think like libertarians when considering what freedoms children should have. And allowing unfettered access automatically extends to kids.
They mention the example of age verification for in store adult content, and hardly anyone has an issue with that. But then they rest their argument on access to legitimate speech also being limited by age verification, and that's the part I find weak and unconvincing.