Obviously in a social/work environment one would use an individual's preferred pronoun out of courtesy but as has been pointed out most of us won't even encounter this very often (nor have to announce his/her/their own). However, there are other complications. Where someone might have gender dysphoria and would need help and support, someone else might just like to wear a wig and dress sometimes and go by a female identity, depending on how they feel that day. It's interesting there doesn't seem to be a difference between transvestite and transsexual anymore and everyone is transgender. Transsexuals, as I understand it, are allowed access to female only spaces, but there are calls this policy should also include anyone who has no desire for hormonal treatment or surgery.

Sex is immutable and as such one denies a material and objective reality when one calls a "he" a "she" (or vice versa), but in a lot of cases this is manageable. But a number of sex based rights, especially with regard to women only spaces are now being drawn into the argument. It's an interesting one, as well as nuanced and sensitive, which is probably why on this forum (and elsewhere) it's turned to carnage.