I accept that, but you've yourself hit on the reason why the Confederate flag is groan inducing to many.
Perhaps my schtick in this thread was too heavy, but I wanted to convey the point and the caricature of one that defends this view that there is any good reason to fly the Confederate flag or the other side -- boasting about the victory.
When one flies the Confederate flag, it is necessarily digging up old bones and dividing those of us that live in the United States of America, all 50 states, of all colors, of all races, striving to make this a better nation. It's not that we should not acknowledge the event, but that we should do so with the perspective of where we are today. Would the United States be better if the South had won? Would we be better as a nation divided? What would the world look like if the South still had slavery today?
Do you see where I'm going with this?