Actually, we do not know that there's no alien invasion headed for Earth. Presumably most Kryptonians are dead, but some may have survived (like the minions who turned up earlier to free Zod), and even a handful of Kryptonians would be quite an invading force -- look what Zod and Brainiac managed together. Moreover, there are other dangerous aliens in existence in SV's universe, like the energy-eating alien, and the bone-eating alien and Titan, whatever he was; any of those species, and more, might have invading forces on the way. Lex knows alien life exists, and that it can reach the Earth, and he has more than ample proof that at least some of it is utterly hostile to the human race -- so, yes, under those circumstances, I think that some latitude in following normal rules is called for. The end doesn't always justify the means...but sometimes it does, and saving an entire planet is a pretty significant end. So if Lex has to lock up and study some dangerous people (and he only seems to keep the dangerous ones confined, hence the farmer he merely studied from a distance until it became clear the guy had been killing people), I don't think that's too high a price to pay. Clearly, you disagree, but that doesn't make me -- or Lex -- wrong. Just...pragmatic.

As for Moira having no moral responsibility to help control dangerous mutants...is that like the people who hear someone screaming for help, and tell themselves that, because they're not cops, it isn't their responsibility to do anything about it?