Have you seen grade school girl's fashion? I honestly don't even know where you would go to buy shorts that aren't short shorts for girls. If you exclude capri pants the longest I have seen is mid thigh and those are usually tighter than the short shorts. It is just the fashion now a days. And if anything the fishnets help hide the legs you are so afraid of seeing.
replace the daddy's lil monster tank with a my little pony tank and jean shorts that are just as short and I have seen girls wear outfits with the same amount of skin showing. Hell, more because they didn't have a jacket over the tank or pantyhose underneath the shorts. It is only sexual if you make it sexual. In the film harley made it sexual, at the con, the little boy did not.
I don't have kids so I don't really pay attention to children's fashions. Plus, tights are not the same as fishnets. ---