Agreed but I think the confusion comes from the world "ability". Any threat to the opportunity to have equal ability in a particular discipline beyond our control (say because you were born a man and therefore will start with lesser ability in [xyz]), will be a theory met with opposition.

If on the other hand we're talking about differences in preference only, leaving ability out of it, the argument is harder to criticise.

Either way, it's crazy he was fired for the memo, it sets a dangerous precedent for staying silent unless your words are pre-approved.