My friend, "Why did it take Christians thousands of years to see slavery is wrong" is the statement of a certified donkey who knows nothing about anything.

Christians since the time of Gregory of Nysa in the 3rd century AD have been arguing against slavery and Exodus 21:26, which you have chosen to ignore by the way, clearly condemns the slavery of the south thousands of years before it happened...a law which Paul, within the first century AD affirms in the NT.

Further, my whole case does not rely on Revelation 18, (which by the way Bible scholars like Paul Copan and even the ESV study Bible have used to make the exact same point)...so the fact you think that's what the whole case for the Bible condemning slavery in the new testament is based on makes me believe you cannot read.

If your Bible is not clear on condemnation of slavery it's possibly because you are still a slave to sin and death.