Stripping each of the two examples down to the point where all you have left to compare them with is the principle of "ends justifies the means", then sure, they're the same. If our categorical imperative was "the ends never justifies the means" then we could stop gathering information. However, I think the specific means and specific ends matter.
You've constructed your example - or in any case could clearly construct such an example - such that the value of the end in both examples is equivalent from the perspective of the person conducting dark arts. However, the, means are clearly different. Framing someone for murder is far worse. That's the moral difference. If you changed the example to radically reduce the heinousness of the means, then I think the moral case is equivalent in both examples, from the perspective of the person conducting the dark arts.
My final thought is that there's a grand hidden "ethical prior" that we're ignoring here. Regardless of the particular end in question, we should take into account the degree to which rational processes were used to justify that end. We can legitimately claim the moral high ground if the opposing side fails to provide any rational justification for the end they are promulgating.
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.