I think it was wrong. But much of the slavery in the bible was not the black slavery of the 1700 - 1800's that we tend to think of. Many slaves in the bible were servants. Many people sold themselves into slavery. Slaves in the Hebrew culture could own property, accumulate wealth, and eventually buy their way out of slavery. This is what I've read. I don't claim to be an expert. So if you know something different than that, I would like to hear it.
Of course modern day human trafficking is a sin. Is a person "loving their neighbor" if they exploit others? Of course not.
I can't imagine that a real Christian would be engaging in human trafficking as we know it today. So I can't accept your assertion that we believe that human traffickers would go to heaven.
If biblical slavery was just serventuide, why did God bother freeing them from the Egyptians instead of letting them buy thier freedom? After all, it's been proven that Egypt never has mass slaves, but paid laborers... not owned, but paid by the state/nation. God frees them from something that isn't that bad, but doesn't lift a finger to help those imported to the US like property whom suffered incredibly worse conditions than the jews ever experienced.