I think you need to re-read the John Stuart Mill quote. You are not presenting your other side in their most plausible and persuasive manner. There are indeed people, and indeed congresscritters and lots of those they influence who said exactly what you wrote, but that isn't the best argumentation that has and does exist on that side of the fence.
Well the best argument perhaps has a place in a philosophical discussion, or perhaps in refining the position to a compromise. And perhaps I'm missing something but isn't the implied step in agreeing to Cap & Trade or SMM indeed listening to the best argument from the other side?
As an intellectual endeavour Mill makes sense, but as a political tool it somewhat misses the mark: the polity of the opposing side actually has to believe and support those arguments. Death panels may not be the best argument but one thing is for sure - it mobilized the base.