I'm interested if anyone was GC right from the start?
The short and smug answer to this is 'yes'. It's a bit more nuanced than that in reality, though.
I first thought about this back in the 90s/early 00s when I was learning about feminism for the first time. I remember Germaine Greer coming out with a book that I devoured that discussed this topic (amongst many others) and I was addicted to the US feminist Ms forums, which at the time was filled with debates about 2nd v 3rd wave feminism. I found myself far more inclined towards the 2nd wavers and particularly those feminists that were describing themselves as radical. The trans issue came up on there from time to time.
So they got to me first, basically. What they said made sense. However, I see now it was a pretty superficial understanding and I hadn't engaged with any differing views or known any trans people. The first time I heard about Judith Butler, for example, was later at university and it was very much in a "some academics go so far as to believe sex itself is a social construct" sense. A fringe idea.
Because it wasn't affecting my life and hadn't entered mainstream discussion, it wasn't a feminist topic I thought about very much at all.
The next time it really came to my attention was around some blue/pink-brain-type research and that made me change my mind. The prevailing view appeared to be that there were distinctions in brains and transwomen's brains were more similar to women's than men's. I didn't like the idea of sexed brains, but it seemed to be accepted, so I accepted it. Again, no deep digging and as none of this affected me in any way I didn't consider what this actually meant for women's spaces, etc.
The third act was hearing a news story on the radio about Chimamanda Ngozi Adichie. She was being labelled a bigot for distinguishing trans women and natal females, and I was incredulous. I couldn't see how what she was saying was illogical, non-factual or discriminatory. She didn't even say trans women aren't women, just that there are important distinctions. Even accepting as I did at the time the pink and blue brain thing, I could see that denying those distinctions was patently ridiculous. I continue to believe that even if there was some scientific revelation tomorrow that proved some commonality between tw and natal females this would be so.
It was the springboard for becoming far more clued up on this issue. I found the brains thing was no longer in favour, learnt about self-ID and the literal dogma that is twaw... And basically came back to my initial position, but based on a more thorough understanding of the issues.
My view of actual trans people has not changed throughout this whole time. I've seen some on here argue that tw don't really face discrimination and have to disagree - I've stuck up for trans colleagues being mocked by others. I think gender dysphoria is a very tough row to hoe. I applaud people who play with gender expectations. And I agree 100% that in most of our day-to-day activities we do not need to know what genitals somebody has. But recognising this, combating transphobia and making trans people's lives easier cannot be at the expense of women's needs.