Diversity Statement???

I checked the mail today, and there was a letter from University of Wisconsin-Somewhere, a thick envelope. So's I open it up, and there is a letter (signed, which could be a good thing, unless she has Margret Atwood's technology) from the library director, saying that she my resume, letter, and references, but that they still need to receive my Diversity Statement. As with the Teaching Statement, I am at a loss as to what this ought to be, aside from: "Diversity is good. I like diversity." Any suggestions?

I don't know whether to play the gay card (assuming they do have some sort of equal protection for homosexuals, which the EEOC form that was also in the envelope should indicate). On the one hand, that is my one claim to being diverse -- otherwise I'm just a fat white guy from Germanic stock -- but on the other hand, it smacks of desperation, like I'm just trying to prove that I'm not as Wonderbread as I seem. And I'm not overly comfortable having a potential employer having that information before I even meet them. But then again, as an undergrad I participated in panel discussions in human sexuality classes and dorms, as a rather ham-handed attempt at "outreach" by the university's gay/lesbian/bisexual/et cetera alliance. Which I suppose was all about the diversity. I dunno.

My question is: how useful are these statements?