In her article, Hayton actually tried to invalidate the concept of gender identity for everyone, not just herself. As she put it:

'Rather like the “luminiferous ether” of the 19th century, a hypothetical substance used to explain the transmission of light, gender identity was invented rather than discovered. But when Einstein showed that ether was unnecessary to explain its existence, that idea was abandoned. Presumably, then, if transsexualism can be explained without a mysterious biological force, gender identity can join it in the history books.'

I would have no problem with it if Hayton said gender identity didn't apply to herself, for example (and there is indeed a small minority of trans people who think that way). But she was clearly trying to force fit her views onto other trans people.

Again, I have no problem with Hayton exercising her free speech. However, she literally was attempting to invalidate the concept of gender identity for everyone. Therefore, other trans people (including myself) using our free speech to push back and point this out is only fair.