I actually did exactly that a few years ago! I was at a neighbor's house and he mentioned that he had heard the civil war actually wasn't about slavery, but was about states rights. So I told him to read the South Carolina Declaration of Secession .
To my neighbor's credit, he actually sat there and read it and then went "oh so it actually was about slavery."
Unfortunately, I can't report that this was a huge epiphany that changed his overall views or way of thinking. This was around the time that Obama was getting his supreme court pick blocked, and my neighbor is still as Republican as ever to this day.