GD is LITERALLY in your head. When you have GD your brain incorrectly perceives your body as 'wrong'. If you need a medical professional (or a group thereof - psychologists, psychiatrists, endocrinologists, surgeons) to help your cope with your condition, you have a medical condition. A disorder. Something's gone wrong.
Being gay requires nothing like that. Nobody comes out as gay and needs the endocrinologist as a result. Nobody needs their bloods taken because they are gay. Nobody needs to perform major surgery on you because you are gay.
The situations are not analogous. People were wrong to call being gay a disease or a medical condition because it's not.
People are right to call GD a medical condition because it is.
If it was not a medical condition, it would not require medical treatment.
But yeah, TRA's can't have it both ways. It can't be 'oh my god access to hormones is neccessary to stop me killing myself' AND 'totally not a disorder'.
If you are trans, and you don't have GD, then dress up how you want but the NHS has no responsibility to fund your lifestyle choices, and society has no need to accomodate your identity.
If you have GD and need a massive amount of medical and social support to manage your condition, don't tell me it's not a disorder.