I'm not sure I've ever met anyone who would seriously argue that the most important thing about them was their gender or sexuality, but then I'm not sure that it makes sense to talk about some property of a person being the most important thing about them.
I've thought about your response and should like to resile from my use of my initial use of 'important' and replace it with what I subsequently implied it to mean:
influential or consequential. I pass over your objection that importance can only be judged relative to circumstance on the grounds that I seek only to address the circumstance of their everyday lifestyles and life choices--those chronic and universal circumstances that we gather under the heading 'everyday life'.
I think also that we have to accept that most people are very bad at seriously analysing their own motivations, let alone identifying the particular strands of their identities that have shaped them. I myself make no claims to expertise, but I have had the 'advantage' (such as it may be) of having spent a few years studying philosophy, and a good few more having lived as a visible minority who encounters contrastive identities, assumptions and
weltanschauungen on a semi-regular basis. My conclusions may be no more valid than the next man's, but I have, at least, come to them
as conclusions: the end-points of considered thought and experience--I'm not just leaking instincts onto a pixellated page.
So if we were to consider how
influential and
consequential some people view their sex and sexuality (it seems to me a growing number, but, like you, I acknowledge this is more based on sense than established fact), it would seem fairly obvious to me that a decent number of (non-pejoratively) 'queer' people, particularly among the younger adult generations, now make major life-decisions with sex and/or sexuality as the most decisive factor. I have no time now (being on a train and a phone) to search for the supporting statistics, but the gay men and women I know (I'm afraid I'm not personally acquainted with anybody transgendered) are
much more likely to have chosen the communities they live in, the subjects they've studied, the professions they've pursued, the faiths they do and do not follow, the people and parties they vote for, the charities they donate to, the places they visit, the hobbies they adopt, whether or not to raise children, the authors they read, the genres of music they listen to, the media they consume, and of course their sexual and legal partnerships
with primary reference to their sex and sexuality than the heterosexual men and women I know are to have done the same thing. Of course sex and sexuality are not the only factors in play, but in most of these areas, they are
quite likely to be the dominant ones. Naturally, there are practical and historical reasons for many of them, but at the same time, if I were to remove all those areas listed above from our consideration of an individual's identity, there wouldn't be a whole lot to go on in the modern world--these are the ways in which most people today express their individuality (some may think it shallow, I think it was ever thus).
Interestingly, I think there's also likely to be a slight increase in the number of
heterosexual men and women for whom sex and sexuality is becoming a more consequential influence on all the fields in that list, but I suspect that any such rise may be due to a more general rise in intolerance and a polar reaction to the same tendency among the non-heterosexual community--but as we agree, this is speculation.