I'm not sure if you really don't understand what you just agreed to. You initially claimed that it doesn't matter what "women" means when you ask, "Do you sincerely believe that a person becomes a woman simply by self-declaring it?"
With a reductio ad absurdum disproof, you've now shown your claim to be false and agreed that the definition of "woman" matters. So if you're still interested in the answer to your question, you may now provide your definition of the word "woman."
> You initially claimed that it doesn't matter what "women" means when you ask, "Do you sincerely believe that a person becomes a woman simply by self-declaring it?"
No, I said it doesn't matter to to the point I am making what I believe, except that I reject that particular definition, because it is absurd on its face. I may or may not reject any number of other definitions of "woman", it's besides the point.
As an analogy (futile, I know): There are many definitions of what a "doctor" could be. For example, I can accept the definition that "a doctor is someone has been licensed to practice medicine". I can't accept the definition that "a doctor is anyone who self-identifies as a doctor".
Of course, according to the definition that "a doctor is anyone who self-identifies a doctor", someone who self-identifies as a doctor is a doctor. It's obviously true and obviously absurd.
> There are many definitions of what a "doctor" could be
Right. So if you ask somebody, "Do you sincerely believe that a person becomes a woman simply by self-declaring it?" you need to tell them which definition of the word you're using, or they'll be talking about something different from what you think they are.
This is, again, absurd. According to the definition that a doctor is a person performing witchcraft, do you sincerely believe that a person performing witchcraft is a doctor? Do you sincerely believe that a true statement is true?
Let me then rephrase the question: Do you reject the definition that a doctor is anyone who proclaims himself to be a doctor? This is, again, an absurd definition of what a doctor, a woman, or really anything could be.
So let me broaden it: Not only do I reject this type of definition for doctors or for women, I reject any such circular definition as absurd. You don't?
With a reductio ad absurdum disproof, you've now shown your claim to be false and agreed that the definition of "woman" matters. So if you're still interested in the answer to your question, you may now provide your definition of the word "woman."