Effective, But Not Good

Atrios writes, in response to an appearance by Biden on Blitzer:

That's a good response from Biden, and it's the same response Democrats should be making not just for anything that comes out of Dick Cheney's mouth but anything which comes out of George Bush's mouth. Dems seem to generally lack the understanding of how effective general dismissive disdain and contempt can be.

No, no, no nonononoo... can I more emphatically say "no"? We don't want to go down that road. The exchange in question was as follows:

BLITZER: All right. You want to respond to the vice president, Senator Biden? BIDEN: No, I don't want to respond to him. He's at 20 percent in the polls. No one listens to him. He has no credibility. It's ridiculous.

Biden is poisoning the well; the popular perception of a person's credibility has absolutely nothing to do with the truth of their argument. Why stoop to engaging in logical fallacies when you can just point out that Cheney is mouthing the same empty platitudes that he always has? Atrios' embrace and approval of such methods highlights a trend which I've touched on here and here, progressive culture's increasing willingness to embrace pragmatism over principle. Is it not the rankest hypocrisy to excoriate the Right for engaging in such behavior and then engage in it yourself? This is not to be taken as a personal attack on Atrios. I don't know the guy and probably never will. But judging a tactic based on its effectiveness is exactly the strategy that keeps the monkeys in power today. Smear John Murtha? Sure, why not? How about Al Gore? I heard that he claims to have invented the Intarwebs... Progressives could engage in the same behavior, and it would probably be effective. I assume that Atrios would not approve of such behavior. But, at least to my eyes, there's no clear line between Biden's behavior and the Right's treatment of its critics... you just gradually ooze your way over to one extreme. Permit me a Star Wars reference: the Dark Side is powerful, and seductive. This is more than a theoretical concern; progressive culture is full of people whose only failing is that they are human. Unfortunately, being human often means succumbing to the temptation to bend the rules a little bit in the present in the hopes of securing long term benefit in the future. Power corrupts, etc. I can certainly be accused of mouthing platitudes at this point, so I'll sign off with this question: What mechanism allows us to embrace effectiveness while staying "not evil"?