The truth will slap them down, hard.
By counting slaves, who didn't have a right to vote, slave states would have had greater representation in the House and the Electoral College. If slaveholding states could not have counted slaves, the Constitution would not have been ratified and there would not be a union. The compromise was for slaves to be counted as three-fifths of a person in deciding representation in the House and Electoral College. The compromise reduced the power of slave states relative to the South's original proposal but increased it over the North's original proposal.
My questions for those who condemn the three-fifths compromise are: Would blacks have been better off if slaves had been counted as a whole person? Should the North not have compromised at all and a union not have come into being?
Know the truth. Stop an Echo. It is important to learn. It greatly increases your capacity to stop these. And we need your capacity to be realized.