UPDATE
@downvoter, if equality isn't a fuzzy premise, where is the line drawn between things that should and should not be equal?
For instance, why shouldn't everyone have an equal opportunity to participate in the Olympics? Why shouldn't everyone have an equal opportunity to be a CEO on Wall Street?
It's because they do not have the functionality that these positions require, as mynameishere pointed out regarding marriage. Claiming equality merely glosses over these important distinctions and does not bring any substance to the argument.