Shit, I don’t even think it has to be subtle. People emigrate all the time for a variety of reasons. And most of them are much less compelling than “I’m surrounded by people who might decide to murder my entire family any day.”
They have no responsibility to stick it out and take the risk just because other people, including myself, don’t want to see the settlers win.
Is the book just the story or does it have the parts where the grandpa is reading the book to the kid?