Great thought about oppression. We do usually see it as a simple matter. But while Christians were using the bible to justify slavery, so too were evangelicals actively opposing slavery, and some historians would contend that theirs was the most important contribution to the anti-slavery movement. Same with science. While the church actively suppressed science early on, it wasn't that long before its power to do this disappeared. Indeed, historians say that Christianity provided quite a favorable environment for the development of science (Gregor Mendel being a monk, after all!).