To use an example plucked at random, it's like asking an atheist ethicist to explain why God allows evil to exist. The theologian would insist that it's a theological question.

Yeah, I don't see what this accomplishes. The Marxist can't pretend that labor market efficiency and healthcare coverage don't exist, and it can't pretend that there is no empirical objectivity to how much labor market efficiency will increase given an expansion of healthcare coverage.

Hm, I'm not sure it's all that interesting to ask, "Let's suppose you're totally wrong, would you then agree that I am right?"

It's a perfectly interesting question. I'm not asking "would you agree that I am right", I am asking "would you agree that the problem with inequality is independent of the LTV argument." Given that some Marxists have actually rejected the LTV, it seems odd that you would find the question impossible to answer. Moreover, you could ask the same thing to other philosophical theories and it would make sense, e.g. if an instance of theft turned out to actually be consensual then it wouldn't be bad anymore.

Alternatively, you might really think the LTV is just a subjective interpretation with no truth to the matter, but if you take that route then any argument based on it can be dismissed merely by saying 'nuh-uh.'

I think your model of philosophy and economics presupposes an underlying objective truth that only economics can reach, and ethics is a layer put on top of that. The argument of Marx is rather that the way economics is constituted as a field is already philosophical and practical and involves ideological and ethical commitments.

This is a strange way to approach things and totally misses the point. I could accept all of Marx's interpretations of the economy and not change a thing about my normative principles. Merely saying that some economists make ideological assumptions (if they even do) doesn't seem to get anywhere close to showing that there's no "underlying objective truth" about what causes what in the economy.

These are pretty standard utopian objections to Marxism, i.e., "You can't think of anything better, and/or you can't think of a way to get there." There is a lot of writing on revolutionary practice on this.

Oh for sure. Plenty of debate. It's tremendously unclear though, which is why I retain plenty of epistemic modesty before making claims about how we should spend all our effort to risk the stability of the global economy, for instance.

I don't quite understand what you are asking here. What is the counterfactual?

The counterfactual is whatever you pose as the alternative course of action. So the question here is how you expect to avoid "upholding the capitalist system" and what you expect to accomplish.