I don't think Article IV section 2 gives them any choice. If they free the slave, they violate Article IV section 2. If they don't free the slave, then they are defacto regarding the slave as chattel property.
This also begs for the question of how any state law in conflict with the constitution can be a valid law?
Didn't think so.
I am now convinced that you are intentionally being obtuse. Many times you have been told that Art IV sec 2 refers specifically to fugitive slaves (that would be "runaway" slaves, escaped slaves, slaves who have left their master and run to a free state, looking for freedom). It is not a blanket statement about the legality/illegality of slavery. In fact it acknowledges that there are states where slavery is legal and that there are states where it is not legal. If that same slave had been brought into Pennsylvania by his master and kept in that state for over six months he would automatically become free by the state laws of Pennsylvania. Even George Washington understood this. Even the slaves understood this. Even Ichabod Crane understood this. You are apparently the only American who does not understand this.
Regardless, Taney (like Herod) settled the entire issue once and for all by deciding that blacks were not citizens, had never been citizens and never could be citizens. They were, as he said, a lower order of being than the white man. How did that work out for him? Within a scant two years the country entered into the largest bloodbath the world has ever seen.
ps Please don't drag out your pointy 3D graph/chart. You're gonna poke your eye out with that thing.