Similarly, it is absolute nonsense to believe that that same Constitution contains within it the authority of the national government to mandate that the states permit the killing of unborn babies.
The original intent of the Constitution was that slaves were property. The original intent of the Constitution was that the federal government had no authority to mandate nation-wide protection for abortion.
It's really not all that complicated. It only seems so because so many people deny what I am claiming above and wish the Supreme Court to make stuff up.
Most of the Founding Fathers, including Washington, Jefferson, Madison, slave owners, looked forward to the end of slavery. See the Wallbuilders on The Founding Fathers and Slavery.
To say that the Union Civil War effort was unconstitutional is obviously incorrect. One of the purposes of the Constitution is "To provide for calling forth the Militia to execute the Laws of the Union, suppress Insurrections and repel Invasions"
I don't think "intent of the Constitution" should be the precise terminology here. More like the "effect" of the Constitution. The Framers argued vigorously over the slave vs free question, and the decision to continue to allow slavery (although the importation of slaves was to be discontinued by law in 1808) was regarded as a compromise in order to secure the agricultural southern states into the Union for the common defense—needed to keep England from reasserting itself over the U.S.
The southern states were major exporters to Europe, which greatly wanted timber, textiles and other southern products. The slaves were necessary to the production of agricultural products until the Industrial Revolution in the latter half of the 19th century; the fledgling country struggled over labor costs just as today's fat cats want to force this nation to accept illegal immigration and Hb1 visas so we can compete globally against nations in which the workers are little better than slaves—a situation Trump is trying to address by adjusting trade regulations).
Back to the Constitutional Convention days — certainly slavery ran afoul of the sentiments of the Quakers of Philadelphia who were greatly influential over the Founders, as well as the delegates from the Methodists (a labor movement), the Puritans, and several other denominations populating the northern colonies. If slavery was their "intent", it was only very reluctantly so.