I think he meant that a potential chilling effect on discussion of such regulation is the likelihood that objectors would be labelled as sexist, thus being ignored as opposed to having their points debated upon their merit.
Logically speaking it's the other way around. People who are for this law are sexists (they want discrimination on the basis of sex) and the people against it are the non-sexists (appoint purely on merit). Obviously it will be inverted in many discussions: Orwell didn't invent the term doublespeak for no reason.