Not everybody conforms to the gender binary that Facebook makes us choose between. Everyone should have the right to not reveal their gender, or select a neutral option that replaces "his/him" and "her/hers" with the appropriate gender-neutral pronouns. Even when one selects to not reveal their gender in their profile Facebook still applies gender-specific pronouns to their posts. This is inappropriate and disheartening for gender-neutral and gender non-conforming individuals.
Many individuals who do not conform to the gender binary, whether identify as transgender, cisgender, trigender, genderqueer, etc, do not wish to use gender specific pronouns. These people should be accommodated.