Thanks for the detailed reply - I'll try to respond to each of your points.
First of all, using dark arts does not imply you have to tell outright lies.
Secondly, you say "if a person ends up with better ideas but all the same biases, their heads can later just as easily be filled with whole new sets of bad ideas by other Dark Arts practitioners." When the alternative is that they only had bad ideas in their head, this is a still a win. And your example is the minimum win possible. What if we used dark arts to help someone remove a cognitive bias? Is it now justified?
Third, PZ Myer chose a very effective persuasion strategy, The Admirable Admission Pitch. However, one case where someone was effective sans-dark arts hardly proves the sans-dark arts approach is optimal in general. When you look at a heavy-weight persuader of the world like Al Gore, you can see he makes heavy use of the dark arts.
Finally, you're correct with respect to the problem you pointed out in your 1st paragarph. I'll tweak the post to fix it.
When you look at a heavy-weight persuader of the world like Al Gore, you can see he makes heavy use of the dark arts.
Yes, this is one of the reasons I have serious doubts about global warming.
The product of Less Wrong is truth. However, there seems to be a reluctance of the personality types here - myself included - to sell that product. Here's my evidence:
We actually label many highly effective persuasive strategies that can be used to market our true ideas as "dark arts". What's the justification for this negative branding? A necessary evil is not evil. Even if - and this is a huge if - our future utopia is free of dark arts, that's not the world we live in today. Choosing not to use them is analogous to a peacenik wanting to rid the world of violence by suggesting that police not use weapons.
We treat our dislike of dark arts as if it's a simple corollary of the axiom of the virtue of truth. Does this mean we assume the ends (more people believe the truth) doesn't justify the means (persuasion to the truth via exploiting cognitive biases)? Or are we just worried about being hypocrites? Whatever the reason, such an impactful assumption deserves an explanation. Speaking practically, the successful practice of dark arts requires the psychological skill of switching hats, to use Edward de Bono's terminology. While posting on Less Wrong, we can avoid and are in fact praised for avoiding dark arts, but we need to switch up in other environments, and that's difficult. Frankly, we're not great at it, and it's very tempting to externalize the problem and say "the art is bad" rather than "we're bad at the art".
Our distaste for rhetorical tactics, both aesthetically and morally, profoundly affects the way we communicate. That distaste is tightly coupled with the mental habit of always interpreting the value of what is said purely for its informational content, logical consistency, and insight. I'm basing the following question on my own introspection, but I wonder if this almost religiously entrenched mental habit could make us blind to the value of the art of persuasion? Let's imagine for a moment, the most convincing paragraph ever written. It was truly a world-wonder of persuasion - it converted fundamentalist Christians into atheists, suicide bombers into diplomats, and Ann Coulter-4-President supporters into Less Wrong sycophants. What would your reaction to the paragraph be? Would you "up-vote" this work of genius? No way. We'd be competing to tell the fundamentalist Christian that there were at least three argument fallacies in the first sentence, we'd explain to the suicide bomber that the rhetoric could be used equally well to justify blowing us all up right now, and for completeness we'd give the Ann Coulter supporter a brief overview of Bayesianism.