Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers, which shall be determined by adding to the whole Number of free Persons, including those bound to Service for a Term of Years, and excluding Indians not taxed, three fifths of all other Persons.
learn your history
It was in determining rights, accountability etc... it did not deem someone as 3/5 human... it was all about the representation and taxation under the government... I.E. the rights.... but if you will notice it said "all other persons".... not that all others were redefined as 3/5 human...
Granted slavery was completely wrong (goes without saying usually).. and it was the repression of rights...
But at least get your argument straight... and recognize it was about rights, as this is about rights... .and should not be about the redefinition of marriage, but rather the government recognition of the other types of family unions