I think that you just disagree with the idea, which is fine, but you might consider attacking it on its merits from the perspective of the people who agree with

I think that you just disagree with the idea, which is fine, but you might consider attacking it on its merits from the perspective of the people who agree with it, not have a meta-discussion about when it arose in his mind, how "immature" it is, etc. Norquist, the Republicans who sign the pledge, and the voters who demand it all apparently think that it's a good idea, it's been effective from their perspective, and it's ideologically consistent, so having someone who doesn't like its outcome call it "extreme" and "immature" doesn't really mean anything. It's just another flavor of ad hominem attack.