I think Nov71 speaks some sense here.
As a piece of SLF, even I can see that the Captain had little choice but to enforce the rules. I can also see that putting this down to simple political correctness was, as usual, journalistic licence. The Captain in no way deserves to be criticised or villified for enforcing the rule.
However, as Nov71 says, that doesn't mean people shouldn't be critical of the rather unfair and inconsistant rule itself. I would agree that a far better way of handling this (and ensuring any child seats used are up to standard) would be for the airline to provide them at an appropriate charge.
Bobbsy