They are scientists, trying to discover moral truths.
This doesn't really fall within the realm of science; all the aliens discover is the subject's
perception of morality--which is different for just about everybody.
For the purposes of this hypothetical, the 'Law of pushing a button' is at least equally rigorous to the 'Law of Entropy'. That's what that comment referred to. If you're ignoring a stipulation, you're not engaging the hypothetical in any meaningful way.
This
is how I approach hypotheticals: with skepticism. When confronted with a situation that seems wierd, contrived, too good to be true, or whichever, I immediately suspect foul play right off the bat. That's the reason I never get taken in by all those Nigerian princes (Niger certainly has a lot of princes lately, doesn't it?

) who say they need to move money out of a bank. When I'm confronted by a world leader who is a religious nut and is threatening a nation that has a hundred times his military strength, it's clear to me there's something screwball going on. The dude is acting like a complete idiot, so it's almost certain he has a motive that is not what it appears. And when aliens contrive a situation where a person is forced to kill somebody, there's obviously hijinks going on here as well. Why experiment on us instead of themselves? Why learn about
our moral limitations? Could be a prelude to an invasion, in which case the best choice is to give them as little information as possible.
Further: the victim who is being "forced" to choose who to kill in this hypothetical, can't really be forced. I could simply look at my watch; if the second hand is on an odd number, I push red, and if the second hand is on an even number, I push blue. So I'm not choosing to kill anybody; it's entirely random, and the fault for the murder lies on the alien dirtbag who fired the mind ray. (If I don't have a watch, I know other ways to come up with a random number--the 3x+1 problem is a good one)
Random side note: when one is in a (hypothetical or not) situation where one is being forced to kill somebody, isn't there a moral imperative to try and find a way out of a choice one should not be forced to make....?
On a separate note: If you saw all possible futures of a person, would that not be clairvoyance in your opinion?
Then how would I know the difference between clairvoyance and a fertile imagination? I can already see many possible futures for things, even though I'm pretty sure I'm not clairvoyant. For one, I can see
your possible futures. After you read this post, either you'll write something disagreeing with me; or you'll write something along the lines of "oh, yeah, that makes sense"; or you won't reply to me at all. In any case, you'll experience the desire to do something not on the list in order to spite my prediction.

DizzyBlizzy had some fun with that earlier on.
Obama might win in November, or (more likely) he'll lose to Romney, or (less likely) he'll lose to Santorum.
Iran is pretty likely to get hit with airstrikes very soon, but it's also likely to go nuclear because other nations are being cowards and are not willing to deal with the problem. Global warming could destroy the planet, or do absolutely nothing significant, or turn out to be beneficial, or (most likely) cause a random hodgepodge of good and bad things.
Was any of the above stuff clairvoyance on my part?

Nope. It was simply the active imagination of somebody who has too much free time on his hands.......