[DoodleDawg]

This provision of the U.S. Constitution was widely unenforced in the North, as were the various Federal Fugitive Slave Acts and numerous affirming Federal court decisions

I'm still not seeing how this qualifies as "tyranny" under the commonly accepted definition but maybe that's just me.

You yourself mentioned how the federal government passed laws to ensure Article IV was enforced. That doesn't sound like tyranny to me. The Fugitive Slave Act of 1793 and the Fugitive Slave Act of 1850 were both meant to strip fleeing slaves of any legal protections they may have had. So it isn't non-compliance that the Southern states complained about, it was the fact that they thought that the fleeing slaves had habeas corpus rights and the protections of the court which guaranteed them a fair legal hearing before being extradited. Southern states couldn't handle that. Also you complain that the Northern states didn't enforce the law. But the Prigg v. Pennsylvania decision made it clear that federal laws were federal responsibility to enforce, and that states could not be compelled to do it for them. So maybe if the federal government forced the states to do their bidding, that might have qualified as tyranny. But they didn't.

Of course, the long-standing animus between the North and the South also involved other issues unrelated directly to slavery, such as the protective tariffs and non-tariff restrictions on imported machinery and the “free soil” movement.

Again, where is the tyranny of an oppressive and overreaching federal government in any of that?

[riverdawg]

It is true that the federal government, and some state governments in the North, had laws on the books that nominally enforced Article V. But these were widely ignored are rarely enforced against those harboring or abetting the harboring of escaped slaves. There were clear moral reasons for this widespread, open, and personal nullification of the Fugitive Slave Acts among citizens and their elected officials in the North. But the bottom line is that many Southerners viewed such nullification as a form of tyranny by federal and Northern state officials, much like some of us view many of President Obama’s executive actions as a form of tyranny.