The researchers are aware that women on average perform worse than men, even given the same resume. As a general principal, this is not ridiculous, e.g. a female boxer will perform worse than a male boxer, even given the same height and weight. You personally might believe that a resume so perfectly captures the qualities of a person, that the person's gender is no longer relevant once you have seen the rest of the resume. But that is just your opinion.
So the professors are discriminating against women, but not for its own sake, but because they believe that statistically, even given the same resume, the woman would on average perform worse. See http://en.wikipedia.org/wiki/Statistical_discrimination_%28e...
This kind of discrimination does not actually make women on average worse off, in the sense that it only penalizes them for their actual inferior performance, not for being women per se.
On the legality, I don't know if it is legal or not. I'm guessing it is illegal but in my opinion those laws are wrong anyway.