Well, he didn't speak out against it either, did he?
The closest he gets to anything about slavery is the Parable of the Unforgiving Slave (Servant in modern translations). He doesn't call the king in the story out for owning a slave (the ungrateful guy is a slave, not a servant). He says the slave was bad because he didn't forgive the other slave the debts.
he didn't say "hey, owning people is bad!" he said "you should let debts go."
Also. IF the entire bible is the Word of God, Paul's letters to the Ephesians. I mean. He straight up says "hey, Christians Slaves, you need to listen to your Christian Masters."
WTF?
Christ may not have ownes slaves, but he didn't do anything about it.