If it's actually caused by them thinking he's a woman, then sure, we want to be more aware as a culture of our treatment of people. If we're just assuming that's the case when there's no indication that it is, though, that's not understanding anything, that's confirmation bias.
Or it could be that they just think he's wrong and a woman. My point is that we don't have any indication one way or the other and it's intellectually lazy and dishonest to just jump to the conclusion that verifies our narrative without ample evidence that we should. When we assume situations will fit our preconceived notions without evidence we're doing nothing to combat our own confirmation bias. If we care about honesty and accuracy we should try to disprove our assumptions, not prop them up.