I'm sure Lex does his best to persuade people to help fight the coming alien hordes, just as he tried to persuade Moira. I'm also sure he succeeds in persuading quite a number of them, and perhaps in buying the cooperation of quite a few more. But Moira, with her particular ability, was a unique case, and he needed to pull out all the stops in an effort to recruit her. So he tried polite persuasion, and the carrot-and-the-stick routine, but -- to her discredit -- all Moira would respond to were threats, so he finally used those. He didn't succeed (more's the pity for the Earth), but he tried, and I cannot blame him for that. There are a lot more lives than Moira's and Chloe's in the balance, and when/if the aliens come, they won't make sure not to hurt Chloe and Moira just because they refused to help Lex save the world.