You aren't familiar with Christian doctrine are you? All men are sinful. The bible is clear on that. You can't judge Christ by the sinners he saved. "The heart is deceitful above all things and desperately wicked; who can know it?" Jer. 17:9 That only reinforces Christian doctrine which our founding fathers clearly saw in forging separation of powers and checks and balances. That's also why all are doomed to judgment without the righteousness of Christ.
What does that have to do with the Bible's endorsement of slavery? Why would it be a sin do do somthing that is sanctioned by the Bible?