The whole "but they owned slaves" argument is a really bad one. Slaves, particularly black slaves, were not even believed to be human but more like "livestock". Everyone had a horse and put it to work just the same. When people finally understood that these were human lives every bit as intelligent and worthy of living along side society as "people", that is when the events that caused the Civil War began. I don't think anyone needs a history lesson on how it took the founding of the Republican Party to end slavery.