The PC crowd never acknowledges that the United States did not establish slavery in North America, we ended it. Slavery was the product of European Empires trying to make more profit from their colonies. Firmly implanted in the U.S. at the time the Constitution was ratified, efforts to end slavery were culminating when the war between the states started. Any historian worth their salt acknowledges that slavery would have ended before the 19th century without the war, and race relations today would be much better.
I guess waiting another 40 or 50 years might be poor consolation when someone owns you and your family. That being said, the 10th ammendment SHOULD have been defended. It's really too bad that our forefathers picked that particular issue on which to take their stand and to attack a federal fort.
Unfortunately for your rosy thesis the Slavers were bound and determined that slavery not end. That is EXACTLY why they started the war.