The basic argument that most people responded to was the claim that the ipv6 transition was practically impossible. The central point of the counterarguments is that since djb's article, a lot has changed and there now actually are sensible transition plans. Even djb has acknowledged that fact.
The remainder of the arguments were mostly about taste. He accepts NAT; many others argue that NAT is horrible and he ignores those arguments based on straw men (an edit in the original article) like:
(Update 2011/04/02: A lot of people have criticized this
article by talking about how nasty it is to require NAT
everywhere. If we had too much NAT, the whole world would
fall apart, [..]
Moreover, his arguments included technical errors that limit their applicability. All in all he was simply far from convincing. Getting into a discussion where you defend the virtues of NAT is not saying something "you can't say". It saying something unpopular that needs good arguments, because there are good reasons it's unpopular.
The remainder of the arguments were mostly about taste. He accepts NAT; many others argue that NAT is horrible and he ignores those arguments based on straw men (an edit in the original article) like:
Moreover, his arguments included technical errors that limit their applicability. All in all he was simply far from convincing. Getting into a discussion where you defend the virtues of NAT is not saying something "you can't say". It saying something unpopular that needs good arguments, because there are good reasons it's unpopular.