Or there could be a dialog option when a PC is referred to by their apparent gender that the player can select such as

"I'm not a SHE"
"I'm not a HE"
etc.

and then the NPC could reply

"Oh yeah, really? Sorry about that. Well anyway, let's get back to our conversation about saving the colony of Tieflings from certain death by the goblin horde..."
or
"Oh...well that's not really my concern, but I DO think we should get these tadpoles out of our heads before they turn us into MindFlayers! Shall we carry on?"