But I cannot agree that DSDs have ANY place in the transgender argument.
They are though, because the are part of the whole structure of the belief system. It's not just that some people make direct arguments, in it's more sophisticated forms it's an indirect argument that's being made.
One example being the with regard to the idea that there is this thing called gender identity which is separate from sex. Some people, even some psychologists, think that because it is possible to have a person who is technically male, but who has a "real" self-identity as female - and what's more this is socially recognized so not some crazy fantasy - this is evidence that somehow gender identity is separate from or can form apart from our experienced of a sexed body.
So, because we know there are people with DSDs who are biologically male but identify as female we can extrapolate some kind of capacity for gender identity that is separate from the sexed body itself.
Since most of us don't want to deny that, people trying to push gender ideology find that's a powerful argument with many people, and then they use it to argue that there are other situations in which people might experience this different gender identification.
So it's not just the argument that being transgender is a dsd, it's this argument about the existence of a kind of gender essence which can in some cases be experienced as separate from the body. Dsd's are just evidence of that in this scenario.
Someone needs to do the work to really dig deep into this idea of gender identity - our sense of ourself as male or female - and how it's formed, IMO. Because the idea of some essence is just a bad conclusion but seems compelling to a lot of people who should know better.