When defenders of the ball-sprawl feel their rights are infringed upon, I wonder if they have ever been exposed to the rules women have been subjected to about leg placement. Entire etiquette lessons are devoted to the virtuousness of the ankle cross and the vulgarity of the "European leg cross." A woman can be labeled a whore simply by the positioning of her legs. In this sense, manspreading is a manifestation of gendered territorial entitlement; it taps into, if you will, the male privilege of taking up physical space.
There's quite a big distinction between someone wearing trousers and having their legs apart some distance, and someone wearing a skirt or dress and having their legs apart.
For obvious reasons, there's certainly no chance of seeing someone's underwear or genitals if they're wearing trousers, man or woman.
If you had men wearing skirts, or dresses, or even skin-tight form-fitting trousers, and they were spreading their legs in such a way as to make their genitals prominent, then it would be a considerably bigger issue.
The main offence to take here is that people are taking up so much space for themselves on public transport, preventing others from sitting down or also sitting in comfort.
A few idiots sit with their legs so far apart that it's vulgar. It's hardly the norm.