But if you divorce gender from biology, how do you even know what male/female is?
Since male and female are typically distinguished by their genitals* do we need to know this? Like, should people be forced to socially advertise their genital structures?
@The Hammer brought up sex and medicine, and he's right: but in both cases best practice is good communication. If you are dating someone, get to know them before you sleep with them. There's nothing wrong with a one night stand, it's just risky and if their genital structure is going to be a problem for you, best not to do it, eh?
*Biologically, sex is more complicated than gonads and genetics. There are hormones and brain structures involved, as well as psychological characteristics that these influence. It just seem to be the gonads people get all interested in. They say it's genetics as well, but I don't think anyone would care about that.