Well RPF, there are several schools of thought on this subject.
One being that it is culturally acceptable for black men to like biggger women. Also, like someone said beggars can't be choosers. And due to blacks not having as much power or money as whites, it is only natural for them to not be able to have the pick of the litter as much as whites. Please remember folks, this is a generalization, there are thousands of exceptions to the rule.