It is ironic to come from a modern sentiment, a privileged hindsight, in which such a great triumph has been made over slavery partly by means of Christianity and to patronize people who were part of the uphill struggle against slavery, as if we would not have had the same internal struggle and then to imagine all of slavery is invented in the Bible and by Christianity! Such insight lacks any historical context and so is not.
The Bible also is not the issue. It has indeed been a tool of the abolitionist, but the OP is somehow blissfully unaware of that History. The OP has claimed that the churches have been mislead by the Bible, but the Bible is a collection of books and letters that makes no guarantees and is unaware of itself as a whole. Nowhere in the Bible is there a statement that declares what the Bible is for, but the OP has implied there is as if it were a single book, which means the OP is generally uninformed about Christianity and its history and cannot make informed comments about it.
The conclusion of the OP is to flush Christianity, because slavery co-existed with Christians. Many Christians were slaves. Many were born in slavery, but in their way they fought against it. They fought it through Christ, perhaps not knowing that they were fighting it but many did know. Slavery is a recalcitrant and inventive foe, and so the struggle has been epic. Even as the Spanish conquistadors subjugated the South American continent and brought priests with them to impose religion, and as the burgeoning slave trade with Africa was just beginning the foundations of modern freedom were being completed in Christian Europe which would bring about the end of that same oppression. A flame of freedom would eventually sweep through the world and is now burning in most places. Today even where there is slavery people have at least heard of a different way of life. They now know that life doesn't have to include slavery. That's because of Christianity not in spite of it.