Yes, they fought for the freedom to enslave people. Don’t believe me? Watch this video by the head of the history department at West Point:

Also, even if we accept your argument that the difference is in winning, the United States won. Thus, if you revere the confederate flag, you are celebrating a revolt against the United States. You don’t see me raising the Union Jack in my yard. That’s because I’m a proud American, loyal to the United States. Raising the stars and bars says you are proud of and loyal to something else, namely something that engaged in treason against the United States.