Actually I was suggesting you use a qualitative approach (which is what the quoted section says). I don’t think I could come up with a quantitative model that I would believe over my intuition, because as you said the counterfactuals are hard. But just because you can’t easily quantify an argument doesn’t mean you should discard it altogether, and in this particular case it’s one of the most important arguments and could be the only one that matters, so you really shouldn’t ignore it, even if it can’t be quantified.
Actually I was suggesting you use a qualitative approach (which is what the quoted section says). I don’t think I could come up with a quantitative model that I would believe over my intuition, because as you said the counterfactuals are hard. But just because you can’t easily quantify an argument doesn’t mean you should discard it altogether, and in this particular case it’s one of the most important arguments and could be the only one that matters, so you really shouldn’t ignore it, even if it can’t be quantified.