Oh, I agree, but that wasn't Grant's doing. He didn't have the intellectual capacity for political theory! Just a soldier from the Midwest. And the best sources indicate that the stories about his drinking were exaggerated.
Grant was an effective general (whatever you think about his casualty rates, which were certainly appalling by contemporary standards), and he was a good man. Decent people of his time, North and South, respected him, and so should we, even if we believe he was mistaken in opposing seccesion.
Recall that Grant got the job when the Union Army was languishing - and sentiment in the North was to give it up. That would have been a good thing.
I think that the slaveowner Grant (Lee owned no slaves, although his wife did) was a decent general and in a way he helped the south through Reconstruction (he refused to go along with many of the more humiliating proposals). I think he was probably dogged by a huge inferiority complex because he was never anyone's choice to lead the Union troops, the top choices either fought for the Confederacy (Jackson, Johnson, Lee, Stuart) or failed (McClellan, Hooker).