All real little girls' dresses from the '20s to the '60s had been crotch-length.
It was not a problem that little girls' dresses from the '20s to the '60s were crotch-length because children were not yet sexualized the way they are now. 
mnli hypothesis: It was not a problem that little girls' dresses from the '20s to the '60s were crotch-length because children were not yet sexualized the way they are now.  premise: All real little girls' dresses from the '20s to the '60s had been crotch-length.