By not recognizing someone's sex, chosen or not, you are deliberately attacking who they are.[/QUOTE]

Human - Male - Female. Choice has nothing to do with it.
You can cut off your penis, you will still be male. You can cut out your ovaries, you will still be female.
DNA does not change. Your opinion, your desire, your preference, does not matter.

Not recognizing someone's opinion, desire or preference to believe something that is clearly not true is not deliberately attacking them.
It's simply choosing to not participate in a lie. In the long run, you might actually be helping them. Just because you don't like the truth, does not mean that it is not the truth.

The greater mystery is how did a thread about masks in the cockpit get turned into a thread about gender?
I'll come back in a week or two and read all the gnashing of teeth that a simple splash of truth / logic will probably cause on an internet airplane forum.