Personally? I think gender =/= biological sex.

Yes there is only male/female biological sex (with the occasional anomaly resulting in a hermaphrodite or somebody without either genitalia) but gender as a concept is what a person identifies as. If a transgender person feels they are a man/woman even though they were born as the opposite gender, that's fine so long as they aren't letting it become a massive hindrance to their livelihood.

Now, that's not to say that "star gender", or "wolf gender", or "autism gender", or "fae gender" or any other made up gender besides man/woman/bigender/agender should be accepted, in fact you should laugh at people who do that sort of **** because they are wearing gender labels like fashion accessories in an attempt to be the most unique of snowflake.

Basically, as long as people are being reasonable, aren't being massive ******* cunts about it, and don't allow it to negatively impact their life, let the person identify as whatever the hell they want.