Well, to some extent, but that still doesn't mean a reasoning based on it has any merits or justifies a conclusion at all. And in Ham's case, that's even on more than one level.
For a start saying that the aliens were affected by Adam's sin, therefore they're going to hell for it, is like saying that the Amazonian jungle tribes were affected by the nuclear tests, therefore let's make them pay for it. Affected does not mean responsible.
Second, it undermines his own other argument against catholicism. He contended that if there wasn't a literal Adam and Eve to sin and bring death into the world, then it makes no sense to hold on to the rest of the doctrine that flows from there, and basically a big case of 'then how do you explain it all?' But here he argues that it's possible for God to punish beings on planet A for something that happened on planet B. So then that argument works in reverse too: God punishes humans for what some gray 'Adam' did on Planet X.
Sure, it feels unfair if WE are on the crap end of that stick, but then it's equally unfair when applying it to other beings anyway. But in any case, he just provided a way out of his other dilemma, making that other argument worthless.
And essentially going by postulates or not, you can't have two mutually contradicting arguments both be true.
Third, the argument that we shouldn't go there because we can't save them is illogical in any case. We can't convert oil to worshipping Christ, but we dig for it anyway, don't we? I doubt Mr Ham would be very happy if we took that thinking to its logical conclusion and stopped looking for coal and oil because we can't proselytise to them.
The fact is, there are tons of other reasons to look for stuff, and crossing one off the list -- even by bare assertion -- is still not doing much to the rest of the list.
