I agree with most of what you said. That's one of the reasons I gave the historical example of SO2. The claim being made by the person I was responding to was not a remark about net gain but the claim that regarding "Good quality government policy" that "There is no more evidence for that than there is for God" and then backing it up with an argument from irrelevant authority. So giving examples to show that's not the case accomplishes the basic goal.