"I don't see the problem with teaching both sides of an historical dispute"
OK,then would it be all right to teach the Nazi view of the Holocaust in the interest of fair and balanced treatment of an historical issue?
I have no idea what they could possibly say to justify what they did but only presenting selected facts is never satisfactory.
The truth will always out if all information is available.
Apples/oranges, slavery sucked but it wasn't genocide.