First, you must understand that what is being discussed is access restriction; that is, a definition of "pornography" such that material declared to be "pornographic" must be accessed only via an .xxx TLD.
Second, you must understand that a community is a local jurisdiction. Within that jurisdiction, the definition of "booze" and "pornography", for the purposes of access restrictions, can be well-defined.
The Internet is not a local jurisdiction. The only way that you can avoid having "pornography" being available outside of the .xxx TLD on the Internet is to declare that *all* material that *any* authority declares to be "pornographic" must be placed within the .xxx TLD.
In other words, the effect of what you are advocating is that the standards of Tehran are to apply to an Internet cafe in San Francisco.
This problem with variation in standards stymied an attempt to achieve a national concensus in the USA on what constitutes pornography that needs to be access-restricted. Remember the ill-fated Meese Commission?
Internationally, material that is considered vile pornography in the USA is considered to be "art" in certain other countries. Material that is considered to be ordinary in the USA (such as a photo of you with your wife with her head uncovered) are considered to be vile pornography in Tehran and Mecca.
What about the romance novels that adult women (and teenaged girls) consume in vast quantities? Many of these contain material that would make a Playboy reader blush.
More to the point: I'll wager that I have a very different definition of what constitutes "pornography that should be locked inside the .xxx TLD" than your definion.
How dare you expose my kids to this vile pornography that you choose to exclude from the .xxx TLD?
How dare you deny my kids access to art, literature, and medical information that you misguidedly placed within the .xxx TLD?
Simplistic answers to complex problems turn out to be not as simple as they seem.
-- Mark --