Tell me why should slavery should be outlawed and it's wrong

The first major argument of the abolitionists was that slavery was anti-Christian. Genesis 1:27 stated that man was created in the image of God. Aabolitionists supported their position by drawing on the ideals upon which the nation had been founded. Slavery (and especially race-based slavery) denied that all men were created equal as stated in the Declaration of Independence. Thus, slavery was anti-American. Aabolitionists attacked the economic benefits of slavery. They reasoned that the slave’s only incentive to work was out of fear for his master.The conditions of slavery were harsh, starting with the "middle passage" where Africans were stuffed into the hulls of ships like cargo. Some fifteen percent of enslaved people are estimated to have died during travel from Africa. In the US the conditions of slavery acted to dehumanize enslaved people denying them even basic rights. The use of native languages was banned, and it was illegal to learn or teach reading and writing. Marriages were banned, and children were often taken away from parents to be sold. It was also common for slave owners to sexually assault enslaved women. And working conditions were long and hard, especially for field workers, and violence was an ever-present part of life. 

You love them i guess