This is actually a pretty important post because a commonly heard argument from some people is that women can't be discriminated against! Because if they were, the god of free markets would sweep in and turn all bigoted firms into bankruptcies.
The thinking goes like this: If a man and a woman are equally good workers but the market pays the woman less than the man, just because of gender, what profit-making firm in its right mind would ever hire any men?
The simple answer is that things are much more complicated than that.
The proper answer can be found here.