Every man who ever owned a slave in the U.S. is dead. Would you say when the last of that cohort died something improved over when the last slave was freed? O

Every man who ever owned a slave in the U.S. is dead. Would you say when the last of that cohort died something improved over when the last slave was freed? Or that killing them sooner would have prevented (or even changed) what was done after Slavery was ended? It's like saying Germany would be better if every Nazi had been shot. Whatever harm those Nazi's have caused Germany was less then the results of killing people on that measure.