This is, of course, a sleight of hand, as Milton should well know. 

The case that being a registrant of a second or third level domain is effectively ownership (apart from a number of specific legal ways in which it may not be) has been established, but the question of whether being a registry for a top level domain is thus the same as ownership, or should be considered as administration of a public asset, is not settled and is *precisely* what is under discussion. 

And the analogy that the same rules that apply at lower levels is a slick, easy, line of generic reasoning that is easily shown to false in operation. 

There is a precise analogy with trademark law here. We allow registration of a combination of generic words as a trademark, but generally not a generic word alone, certainly not for all classes. 

Kathys example, that we don't simply allow TLD owners to just chuck up a copy of BIND on some cheap commercial hosting,