not to sound harsh but does adcom owe anyone an explanation?
as long as they are not being discriminatory (race, religion, gender, etc.), admissions is a pretty subjective process and they have the right to admit or ding anyone don't they?
as far as this situation, my guess is that you probably won't get a satisfactory answer. are you sure you didn't end up rubbing one of the people in adcom the wrong way? for example, most schools will ding you if there is a complaint against you (e.g. were rude to a receptionist, student, heck...even the janitor, etc.). realistically they'll probably tell you that applications have gone up overall and to make the class as diverse as possible, your background was overrepresented, etc. i've never heard of a school giving an admit after a ding before so your only other real options are to try to apply to another school or wait another year (but try to gauge what your chances will be like next year).
anyway, just my 2 cents. i really wish you good luck in moving forward.
RVD.