A transgender person is someone of one sex who thinks they are another sex. And somehow we are all supposed to subdue our own thoughts in favour of theirs. If you think a male is a male, but he thinks he is female, you are supposed to treat him according to his view, not your own. Why?
We are not figments of the transgender community’s imagination; we do not have to participate in their self-definition. If you do not consider biology relevant, that doesn’t mean that we also have to dismiss it.
You can think you are whatever you choose, but that in no way dictates how I have to think about you.