Sure.

There is a doctrine in law called the fruit of the poison tree.

That evidence that was obtained illegally (even with a fair degree of removal) is not valid.

I want that as a defendant.

Pernkopf Atlas is a thing, its origins are tainted, we all know it. Yet it's still used. It is very much the fruit of a poison tree. Even if the externalities are awful there is still lots of intrinsic value there. Nothing in the world is free of that taint, and if it is all that one seeks then were going to have to burn everything.

It may be relevant that 'fruit of the poisonous tree' is not a general law principle but rather a doctrine specific to modern U.S. law, established only in early 20th century as a specific interpretation of the 4th amendment to the U.S. constitution - the evidence policy is entirely opposite in most (possibly even all? It's hard to tell) other places worldwide as well as in classic (e.g. Roman) law, prioritizing the role of evidence in demonstrating truth and facts, and if some person or organization performed an offense in obtaining it, they should be prosecuted separately for that offense, but it doesn't by itself disqualify the evidence.

OK, now I'm utterly confused: I had meant to refute the claim that discussion of slavery was a purely modern thing by providing counterexamples of ancients who had found that economic system worthy of reflection and discussion, so I fail to see how introducing yet another modern (parochial, yet!) thing may be relevant?

(enthymemes can be effective, but they are utterly reliant on people knowing what the hell your middle term may be)