you can source whatever the forget you want
you can ram a spiked carrot up my ass in protest
you can hold me at gunpoint
you can do loving anything
but you can not loving convince me that there are more than two genders
it biologically makes no loving sense, and anybody who legitimately believes that there are more than two genders is a loving headcase
this is directed at anybody who involves themselves with lgbt stuff
Regardless of your opinion on the matter there are those who do identify as non-binary, or believe that non-binary genders exist.
It's no trouble whatsoever to minorly tailor your language to be non gender-specific, and thereby avoid offending anyone of any gender.
If they offer jobs for postpersons instead of postmen, it doesn't negatively impact anyone, and it doesn't exclude anyone.