I believe the problem can be resolved with an introduction of a set of metatags, whose purpose is to classify "potentially offensive" content, such as deliberate cruelty & violence, and porn / erotica
And so we can have:
META content="from 0 to max" name="pornography"
META content="from 0 to max" name="erotic content"
META content="from 0 to max" name="deliberate cruelty"
META content="from 0 to max" name="deliberate violence"

A webmaster fills the content value and it is used by the Internet filters

Obviously, this is not the way to combat child pornography, but with the theoretically legal, albeit somewhat offensive stuff, it may well work.

A central "repository" of metatags for all sites can be created, similar to ICANN or Google Sitemaps.
However, that "repository" should NOT be a part of a browsing process. They check the compliance on their own schedule, similar to how Google checks their sitemaps.

Obviously, this agency should be staffed with people evaluating compliance with the classification system. A fee can be introduced on every domain purchase (as ICANN fee of some 20c per year).
And, of course, there should be effective process of processing complaints from the public.

If a metatag on site is not in compliance with that in a repository, or there are no metatags at all, or the set is incomplete, that domain is placed on "offenders list" and the webmaster is notified.
That agency should have no powers to "freeze" domains, but they should maintain their lists and the Internet filters can refer to that list.

Quite obviously, a webmaster of some hard-core porn site may submit a realistic value of a metatag at the beginning, but then quietly downgrade it later hoping to bypass the browsing filters.

With this system everyone can set their browser filters to an appropriate level. Libraries, schools, government offices, industrial enterprises may want to completely ban any violence, cruelty and erotic content, while individuals may want to set it somewhere halfway (or "full blast" if they want)

The regulations may even go farther - any webmaster who runs a site with "offensive content" right on the main page, would automatically be placed on the "offenders list". (Some porn webmasters do not have the most basic decency to warn the visitors about the content and to keep their wares off the main page!)

There can be several versions of "offenders lists" - one for public viewing and one strictly for the filters, with just a list of URLs.
If someone buys an Internet browsing filter, he can set how often he wants the filter to update the "offenders list"

I believe this system can effectively frustrate the efforts of the Chinese government (and others) to push censorship on others. Because if they want to block the sites, which are, for example, critical of the occupation of Tibet, they would then have to request a mandatory metatag
META content="?" name="against occupation of Tibet"

And, of course, it would look ridiculous

Regards
Oleg