This is actually a great question and shouldn't be asked sarcastically. Especially the "why" part. I don't think the answer is available yet and won't be for a while
I think that the main problems here are two things. Sex and gender are two different things. That's one, and it doesn't fit the trans activists ideology.
The one we're talking about here (this post, not the whole thread) is semantics. For all of human history, until very recently, sex and gender were so tightly entwined there was little point to making a distinction between male and man or female and woman. A person's birth sex determined a ton of stuff about their life, including their gender. That's not the case anymore, at least not here in places with resources and secular values. We've got therapy and advanced treatment options. It's become important to make a distinction between sex and gender, at least under a few circumstances. Our language, however, hasn't kept up. It's gotten a bit obsolete. The difference is utterly unimportant in all but a tiny few circumstances, but sometimes it is important. "Male' and "woman" , sometimes, are opposites.
Tom