There is a certain hypocrisy for saying there’s no difference between men and women for physical performance and psychology, but that a man can have a woman’s brain - and is treated by mutilating the body to match the mind instead of treating the mental illness.
Since most liberals do not base their beliefs on acceptance of a formally adopted written Constitution, or (in the case of moral matters which are not the province of government) acceptance of a written Scripture “to be the rule of faith and life,” it's hard to see how it could be any other way. A liberal may well have core values which he or she sincerely believes, but if those values come in conflict with what is perceived to be proper “political correctness,” it's hard for someone who does not have a formal written authority external to him- or herself to know how to handle those contradictions and conflicts.
Presuppositions count. Forcing liberals to re-examine their actions and understand the presuppositions which led them to those actions can produce interesting results as observers, and sometimes the liberals themselves, realize they are being inconsistent.
Creating “cognitive dissonance” can work.