Oh, and look at these (again):
“When a man strikes his slave, male or female, with a rod and the slave dies under his hand, he shall be punished. But if the slave survives a day or two, he is not to be punished; for the slave is his money.”
—Exodus 21:20-21 (RSV)
The Bible is not just saying "this is how things are done, isn't it a shame?" It's actively telling you that this is what you're supposed to do, that this is the right way to do things.
And speaking of actively being in favour of slavery:
“Let as many servants as are under the yoke count their masters worthy of all honor, that the name of God and his doctrine be not blasphemed. And they that have believing masters, let them not despise them, because they are brethren; but rather do them service, because they are faithful and beloved, partakers of the benefit.”
—1 Timothy 6:1-2
Oh, look. There;s the New Testament saying that slavery is quite alright. Slaves are to honour their masters, and masters to treat their slaves well. The system of slavery is a good one, in other words. Underground Railroad? Shame on them! The slaves are dishonouring God if they attempt to escape slavery. A slave's duty - says the Bible - is to honour his or her master.
While the Bible doesn't say a very great deal about slavery it says quite enough to show, beyond dispute, that God thinks slavery is a good thing.