But how is it any more fair to let three large metro areas override the preferences of most of the rest of the country?
Furthermore, the Constitution can change. That's why there's amendments; quite a few have already gone through, in fact.
The other colonies begrudgingly added this, opting for changes to the wording of the clause to enshrine slavery into the constitution, and did everything they could to violate their constitution until South Carolina wrote them back saying it is best if South Carolina exited.