> But what they collectively agreed to and wrote down was a pro-slavery document. It drastically boosted the electoral power of plantation states by counting slaves. It enshrined a national mandate to hunt down and recover slaves who escaped to the north.
This reading is illogical and ahistorical. Illogical because there is a logical difference between a document that enshrines slavery as an animating principle, and one that contains compromises with slavery to preserve the fledging union between the free states and the slave states. The Constitution is the latter kind of document.
It's a-historical because it wasn't viewed as a pro-slavery document at the time or even decades thereafter. People smarter than I have covered this thoroughly: https://reason.com/2019/09/13/the-anti-slavery-constitution/
To address your specific example of "boosting the electoral power of plantation states," for example, you have it precisely backwards. Today Constitution apportions votes based on the number of "persons" in each state. Then, as now, that includes every person, whether or not they can vote or otherwise have legal rights. And nobody disputed that enslaved persons were persons (and that is how the 1789 Constitution treats them--it distinguishes between "free persons" and "all other persons"). Therefore, the baseline was for each enslaved person to count fully towards representation of the slave states. The free states argued that enslaved persons should be excluded from the count because under the laws of the slave states, they were treated like property. That argument succeeded in part, and the compromise operated to reduce the power of the slave states.
> Clearly, despite whatever lip service they felt they needed to pay to their forefathers, Lincoln's Republicans sharply reconsidered the consensus of the founding fathers, tore up the old rules, and remade them.
What did Lincoln reconsider? Did they reconsider federalism, gun rights, bicameral legislature? There are a whole host of principles underlying the Constitution, the virtues of which were extolled at length in the Federalist Papers. Did he reconsider any of those? What they reconsidered was a compromise that enabled certain states to retain slavery, but which didn't serve as a foundation for anything else in the Constitution. As Frederick Douglas observed, it took almost no revision to the Constitution itself to eliminate slavery. The 13th/14th/15th amendments were all directed at preventing the south from re-establishing slavery and protecting newly freed people.
> And, respectfully: so long as the path we take to reaching a reconsideration of the 2nd Amendment --- a reconsideration supported by a pretty big faction of constitutional scholars! --- follows the rules in the Constitution, nothing has been "canceled". We're using the tools we've been provided specifically for the purposes they were provided for.
We are cancelling one of the most foundational aspects of rule of law, which is: what did the people who wrote this legal document think these words meant? People designed a system with inter-locking rules. They had a design! What does "freedom of speech" mean? What does "freedom of the press mean?” What does "the right to bear arms" mean? If we can disregard what the people who wrote those words thought they meant, because those people owned slaves--if that becomes a valid mode of argumentation when it comes time to applying those rules--then the notion of constitutional governance would become a farce.
To appreciate the problem that arises, compare to how the German constitution handles things: https://scholarship.law.nd.edu/cgi/viewcontent.cgi?article=1.... In Germany, there is an explicit hierarchy of structural and substantive principles that guide constitutional interpretation. For example, Germany is a federal republic, and Germany’s constitutional court interprets the basic law with an express eye to considering federalism concerns, and related concerns such as separation of powers, etc. They take it very seriously over there. In US constitutional scheme, we rely on our understanding of the framers’ Constitutional design to effectuate these principles and serve that same purpose. If we can dismiss the framers’ deliberate design because of their moral shortcomings, then it would become trivial to eviscerate these principles. At that point I’d demand a new constitutional convention because what would be left wouldn’t be worth the paper it’s printed on.