Well, not everywhere allows discrimination based on sex, some US states don't, for example (California just joined that club last year). Plus the EU doesn't eit

Well, not everywhere allows discrimination based on sex, some US states don't, for example (California just joined that club last year). Plus the EU doesn't either. People generally find a discrimination "fair" if it's based on something that you can change whereas an "unfair" discrimination is typically something that you are.