An even biger question: In general, what does it take to prove such a of claim discrimination? How does one establish that an applicant has experienced discrimination and is not just bringing up "sour grapes" after not get an offer?

The whole job application/interview process is a complex system and the reason for a hiring decision defiantly goes beyond a good site visit (in fact, because site visits are usually only given to top candidates one would hope that the site visits for ALL candidates go very well). Since it is so complex, it's hard (if not impossible) to turn it into something that is algorithmic. However, if the system is not algorithmic and there is this vague fuzziness to it, how does one determine if an unfair prejudice occurs? A lot depends on who the hiring committee feels will be a "good fit" for the position. But how does one establish if factors such as sex, race, sexual orientation, religion, nationality, etc unfairly enter into this decision?

Its interesting that the recent Supreme court decision regarding affirmative action at Michigan both allowed for race to be used as a factor in admission decisions, but at the same time shot down using race in a point based (algorithmic) system.