Logan and Hope believed, like Breevort and Gillen, that if Hope can't control the Phoenix the earth ends up getting destroyed. And as we saw on the moon, Hope couldn't control the Phoenix (something she herself admits both during and after) It's similar to the New Avengers in a lot of ways. They're considering destroying an entire planet. Is it murder? Sure. Is it a crime? Sure. Is it wrong? Depends on your perspective on the matter.