My girls are 'princesses'. And my boys are princes. And they are all superheroes, and ratbags, and boofhead, and angels and a thousand other different names in any one day.
They are very specific gender titles. I wouldn't contradict one of my kids if they decided they wanted to be the opposite. But it's not a sexist stance to call them along the lines their genders are, any more then it is for me to call them miss or master, or boy and girl.

I feel that too many parents make mountains out of molehills. If you don't like the term, then don't use it. But don't cast your own perceptions and dispersions on others who do.