I never remember this well, but didn't DKSA address that possible homophobic fear in a sort of violent way with Dick and Catgirl?
I don't actually think there would be a big deal about a girl showing her legs in the 40s. Wonder Woman showed her legs. I think it was far more an issue of nobody considering putting a girl in the role. Not only would a grown man not run around with a young girl as a friend, the idea would be for boy readers to identify as Robin.