My beef with the Washington and Jefferson slave thing as well as other faults -- along with MLK and his faults -- is that the flaws become the focus. My way of looking at historical figures is to look at the accomplishments, then look at the guy. When you see the faults you should go, "Holy crap, they were just these guys, not gods, but lookit what they did!"
This is the way that they look at all western history. They see nothing except the bad things, but accept as a matter of right all the good consequences.