The 3/5 compromise is what prevented slave states from having overwhelming power in Congress. Remember, the South wanted to count them in full; it was those who wanted to end slavery who fought against that. The idea that the 3/5 compromise was about devaluing black people in America is flawed. Unfortunately, the truth requires more complex thought than "the Founders thought you were only 3/5 of a human." That 3/5 was a failsafe that 1) allowed us to form a country which would go on to end slavery, and 2) prevented the slave states from having the Congressional power to stop it
The correct modern response to this is to accuse the critic of hating nature. Label them an anti-environment extremist who apparently just wants to pave over all the trees and flowers in Mississippi.