Quite - it's not as though sexual identity has always been a strict binary between male and female. Other cultures have explicitly recognised different gender identities for ages which makes me think that it's part of the Western Christian cultural identity to only recognise two genders. e.g. Thai culture has a number of different recognised sexual identities and of course, India has the Hijra.

To my mind, people who are anti-trans identities are simply trying to exert control over others rather than having a generous nature and accepting that different people are different.