Chief Justice Taney repeatedly refers to slaves as "property" in his decision, never once referring to them as sub-humans. Where did you find your "ruling" that they were?
Taney was quite correct, under the law at the time, to recognize that slaves were property. This was just a fact.
Where he went off the tracks was in expanding his ruling from the legal status of particular individuals to the legal status of an entire racial group.
He ruled that ALL persons of African descent (whether slave or free) were "beings of an inferior order, and altogether unfit to associate with the white race, either in social or political relations, and so far inferior that they had no rights which the white man was bound to respect."
While he doesn't use the term "sub-human," which had probably not been invented yet, he certainly got the concept across quite nicely.
It difficult to see how his definition of the status of "Africans" differs from the Nazi definition of the status of Jews or Slavs.
Contract is another form of property, an idea form, where the bounds are established in word or custom. Examples are the title to specified parcel of land, or a contract to supply a hundred blankets at a certain place by a certain day. Or more pertinent form in this case: a contract for labor, like those a Major League Baseball team owner gives to a star player, or any player for that matter.
Contracts are negotiable, contestable. When the terms are vague, unspecified, or problematic a contract is more contestable in court than a battle over real property. With real property, the great presumption goes to the holder of that property.
For example, two students come before a teacher at recess. Each claim an abandoned ball that was found in the play lot. Johnny holds the ball. Billy claims he saw the ball first. Proper ruling: Johnny keeps the ball.
Slavery is, to say properly, under natural law, a form of contract created property. The Slave may be held, sure, uncontested by other claimants to ownership of the right to hold him as slave but what when the slave himself challenges that contract?
To enforce the fugitive slave laws, Taney finds that a African negro slave is a form of REAL property, that is not a man able to bring claims before a court like any other man. And to make that African negro slave such a form of real property Taney recasts the original intent of the framers of the Constitution so that any African negro (or descendant) is banned from sharing in that part of the basic rights of men. Thus, by Taney's reasoning, they are not full men. An African negro and descendants are subhumans, not full humans due all the privileges of natural law. In the Declaration of Independence the Founders affirm "All men are created equal", but Taney's logic removes African negros from that word "men".
In his ruling Taney asks:
The question is simply this: Can a negro, whose ancestors were imported into this country, and sold as slaves, become a member of the political community formed and brought into existence by the Constitution of the United States, and as such become entitled to all the rights, and privileges, and immunities, guarantied by that instrument to the citizen?We see that in that set-up question Taney at first limits who he means, and what he means. In the commentary of the ruling he makes that clearer. He is, at first, talking only of those who were themselves slaves when brought here or descended from those brought here in slavery. And he is talking only of the rights due to citizens.
Yet Taney goes on beyond those barriers:
We think they are not, and that they are not included, and were not intended to be included, under the word 'citizens' in the Constitution, and can therefore claim none of the rights and privileges which that instrument provides for and secures to citizens of the United States. On the contrary, they were at that time considered as a subordinate and inferior class of beings, who had been subjugated by the dominant race, and, whether emancipated or not, yet remained subject to their authority, and had no rights or privileges but such as those who held the power and the Government might choose to grant them.There's no getting around it. The reasoning Taney applies is that the FOUNDERS considered African negros to be "a subordinate and inferior class of beings", of a race inferior to the "dominant race". Subhumans.
Real property, like some cow or chicken.
A sad, tragic ruling.