Out of curiousity, has this guy or his prospective done anything that really makes you not want them to be included? Bad grades? Nasty attitude?
You mentioned that this guy wouldn't bring any diversity, what kind of diversity are you looking for? In no way do I mean to be disrespectful, but when I attended Duquesne (I think where you said your chapter was).....it was the antithesis of diversity, in the aspects of race, SES, and attitude. Finding the right balance of diversity might be something difficult to attain.
How does your voting work? Is it ok for your president to overrule the rest of the chapter on this matter? Check over your rules, and if they don't give him this power, call him on it!
Good luck, Tony! You've come this far, don't get discouraged by this wackiness