Why do you think it was so easy for some white people to justify enslaving and mistreating other human beings?

Whelp this is a awkward question but I Think it was because of white people back then didn't think of African Americans as human being because of there skin tone and there primitive technology that they had

Well depending on how you look it you cant really say "white". Slavery has been going on since 3000BC with the Egyptians. It then progressed through the world and through time until it was seen as very common place. It was even wrote in the bible as being a ok thing. And it was even made more "mainstream/known" with the Arab Slave trade which had 3 times the amount as the north american slave trade. So thats why they thought it was a ok thing