You know how many times aliens have saved my world? Because I can tell you for a fact that some of them do a hell of a lot more for my Earth than most humans do. The ones you met sound like they're the kind of stain on the universe that the aliens I work with do their damnedest to stop. I'm sorry that your world didn't have that kind of protection. I'm sorry that you lost your family. But I don't think your brother would want you to become a killer.