"They could have avoided civil war if they had done it properly."
I think you underestimate the evil of the Democrat Party. They have been lawbreakers from the beginning, and still are. The Rule of Law is a joke to them.
In other words, passing laws has never stopped them. When they formed the KKK and tortured and murdered people, there were already laws on the books regarding that- didn't stop them. And it is the same today. Democrats want to pass more gun laws, which their constituents will ignore those in the same way they ignore the 20,000~ gun laws already on the books.
"We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America."
The illegality of slavery is certainly implied in the very purpose for the Constitution in the first place. Not unlike every doctrine that is taught in legitimate churches, such doctrines had to be defined in order to deal with errant teachings. So too with the Constitution- errant behavior not originally specifically mentioned had to be addressed. In most cases, for both situations, the errors come from liberals.
And this is also much like the liberal's stance on abortion. Every rational human being understands that life begins at conception. They know they cannot win the debate by saying that some lives should not be protected, so they play around with labels in order to dehumanize the unborn life. And the extreme ruling on Roe v Wade is one of the best examples of how low they will sink to do so. They found the "right" to murder their own children in the "penumbra" that emanates from somewhere behind the actual words of the Law of the Land. They have long known that without an activist ruling like RvW, that if the issue of abortion was decided where it should be, at the citizen level, they would lose much of what they have been clinging to.
Such insanity is difficult to understand- they are fighting like rabid dogs for the "right" to murder their own children, primarily for financial reasons. Which brings us full circle to why they fought to preserve slavery- financial reasons.
And evil.