He could have said slavery was wrong......he didn't. So much for Jesus and all of the Old and New testament. In fact it supported Slavery which still goes on to this day - yeah, true.
But it's important to get a sense on perspective on slavery.
Slavery in Christian-majority countries ended a long time ago. The British ended the Trans-Atlantic Slave Trade at the beginning of the 1800s.
As far as we know, Jesus never owned slaves. But Muhammad did own slaves and concubines, and he traded in them.
Slavery among Arabs and Muslims started centuries before the Trans-Atlantic Slave Trade and ended in 1962 in Saudi Arabia and Yemen and in 2008 in Mauritania! ... just think about that for a moment: there are some people alive in Mauritania right now who are freed slaves. Makes you think, doesn't it?