There's some interesting discussion at the Leiter Reports over the role of race and gender in philosophy department hiring.
I'm tempted to say that it all comes down to the empirical question of whether the relative scarcity of female and non-white faculty causes otherwise promising students to feel unwelcome in the philosophical community. For if so, that would be really awful, and Weatherson's argument for affirmative action in hiring looks entirely reasonable (i.e. for the sake of "providing an environment where all students feel encouraged to do philosophy."). I'm pretty skeptical of the empirical claim, though.
Other underrepresented groups include conservatives, meat-eaters, and religious people, as Christopher Pynes points out. Should we thus endorse Horowitz's calls to hire more Republicans? I guess it's possible, but I'd expect that there are more important factors besides sharing group affiliations with faculty members that influence students' decisions here! [But what if many students really do feel (perhaps irrationally) discomfort on this basis? Should hiring committees accommodate student prejudices? This seems to be opening Pandora's box...]
Having said that, race and gender do seem to be especially salient characteristics in our society. That's really unfortunate. It'd be much better, I think, for everyone to generally disregard such traits in the same way as we would for (say) eye colour. But given that this isn't where we're at as a society, what is the best way to proceed? Should we act 'colourblind', and hope that students and others follow suit? Or should we play the "identity" game, and hope that we eventually reach a stage where it's no longer necessary?