David Cooper was a person who believed that slavery was very wrong and wanted to make it stop. He thought that every person, no matter what their skin color, should be treated the same and have the same rights.
Imagine if you and your friends were playing a game and one of your friends wasn't allowed to join in just because they had a different color shirt on. That wouldn't be fair, would it? David Cooper felt that way about slavery - it wasn't fair that some people were treated badly just because they looked different.
He talked to other people and tried to convince them that slavery was wrong too. He even helped slaves who had run away from their owners to escape to freedom. David Cooper wanted everyone to know that slavery needed to stop and that all people deserved to be treated with kindness and respect.