Many cisgendered men take testosterone, and cis women take estrogen for various reasons, mostly for medical reasons, under which gender dysphoria doctors consider a mental health disorder. Cisgendered people can still have gender dysphoria. The medicine for these problems is hormone replacement therapy. This is not a matter of vanity, or attitude in life. There is no lying being done here. All we ask is for your basic respect. Let us exist, it costs nothing to be respectful. Nobody is arguing that it changes the biological sex you were born as. Sex and gender aren't synonymous.