A President doesn’t have much choice when it comes to preserving the Union. He owed that duty to each American citizen, including the American citizens who lived in Southern States. The lesson is a simple one: no person or group of persons has the legal right to strip his neighbors of their American citizenship, even if they believe that they have a good reason, like the desire to own other human beings.
What we call the war was just the enforcement of U.S. laws and the performance of U.S. responsibilities in every part of the United States. If necessary, we’ll do it again, but it won’t be necessary. Nearly all Americans are proud to be American citizens and very few want to own other human beings. It’s over.
As pointed out to you earlier, no citizen was stripped of his rights. Secession in no way harmed any rights of persons living under the original Constitution.
The Confederate States wrote and adopted its Constitution by the consent of the citizens.
You seem a bit confused in your logic.