The Terminator Argument for Determinism

Ok, so I saw Terminator: Salvation (a.k.a. Terminator 4) today. It has its moments of greatness, in between sections of mediocrity.
Anyway, there was one thing in the movie which made me think--and I'm pretty sure it was supposed to...the film didn't have a lot of brains behind it for the most part, but this may be one exception.
I saw, within the plot, an argument that might be used to shift the burden of proof onto the libertarian in the free will/determinist debate.
But let me preface this:
SPOILER ALERT



Ok, hopefully you have stopped reading if you plan on seeing the movie and haven't yet.

One of the characters in the film is named Marcus Wright. He learns in the movie that he is a cyborg--a human/machine hybrid, created by Skynet (if any of this doesn't make sense because you aren't familiar with the Terminator series, go to wikipedia.) Marcus sees himself as being completely human; he is, in fact, not even aware that he is a cyborg until about half way through. So, presumably, his judgment and actions appear to himself as autonomous.
However, later on, after Marcus helps get John Connor into the headquarters of Skynet, the main CPU at Skynet reveals that bringing John Connor was Marcus' programmed mission, and that Marcus has executed his mission perfectly, though he was unaware that he was doing so.
This all seems to make sense, in the moment. After all, it is an American action movie, one ought not think too hard in the heat of the moment.
But, if one could accept (and, even better, to argue for) that the case of Marcus Wright is logically coherent, as well as in principle physically coherent, it seems that a somewhat cogent argument against free will could be made.
If it is possible, in principle, to manipulate someone's experience in such a way as to give them the phenomenology of choosing freely when in fact they are not, then there really isn't any way of knowing why this may not just be the way we've evolved.

So, the argument would look something like this (and, grant me that its late and I haven't thought this through too much):

1.Some version of libertarian free will is the most intuitively plausible.
2.We, prima facie, as well as "the folk," find libertarianism about the will to be intuitively plausible, in main part, because of our phenomenology of choice--that is, we deliberate and act on what seems to us to be of our own choosing.
3a.(What we may call, The Skeptical Premise) This phenomenology of choice does not give us reason to favor a libertarianism about the will over a determinist one--that is,
3b. the phenomenology can be equally explained by something like the Marcus Wright story, without any messy science fiction tale (e.g. we may have just evolved to be Marcus Wrights). Ockham's Razor does not favor the libertarian explanation of the Marcus Wright one.
Therefore,
4.Our reason for finding libertarianism about the will loses its grounding, and along with this, its intuitive force.
Therefore, ceteris paribus,
5.Determinism should be the accepted view, libertarianism should hold the burden of proof.

What obvious hole am I missing? I may be accused of begging the question. Well, yeah, I guess that is probably true. But, if we took an anecdotal survey of reactions to the Marcus Wright story, and most found it coherent, then perhaps we could say intuitions about free will are too highly inconsistent to claim that libertarianism is more intuitively plausible than determinism.