[simon_]

I would not write them off - my whole point is that by making the double argument people are trying to avoid having to think about trade offs.

I get very suspicious when I see conjunctive arguments that neuter hard value judgments. It's extremely common to see them: "I think you doing X is objectionable AND it doesn't even work!" Example from the right:

Gun control is unconstitutional AND criminals will still get guns anyway!

In my experience, the second half of these arguments usually has nothing to do with the arguer's real motivations, it just helps him/her avoid cognitive dissonance from the trade offs.