A TestCase is a scenerio, real or contrived, which serves to validate or invalidate a larger, over-arching point.
The Slavery issue was a TestCase of the larger issue of ConFederalism and Federalism.
Specifically: Is the Federal government more important than State and Individual Rights?
The Union won the war for Federalism. But, there has remained strong support for State and Individual Rights guaranteed by the Constitution.
Those who are tearing down Confederate monuments are really trying to destroy the vestiges of State and Individual Rights once and for all in favor of a Socialist system which owns everything and controls everyone.
Slavery has become just a smoke-screen for their insidious plan to destroy Constitutional America.
Don't be fooled. They are not jousting with monuments, they are jousting with the Constitution.