If I were to add something that would make my argument against slavery more convincing I would probably say something like what is the roles were switched, would you want to be a slave?
When people went to Africa or when they bought slaves they would often say something like it was in the bible and because of this that it was okay when this was not true so you could possibly use that to help your argument against it. There are probably better answers out there but I wrote a argument against slavery once and I used this stuff in and got a pretty good grade.
