In the instance of the Phoenix in AvX, it was destroying every planet on it's path to earth. So trying to prevent Phoenix from coming to earth in that instance made a bit more sense. If the Starbrand was actively blowing up planets at the time of the story, they'd probably think twice about taking it to earth in this story too.
But yeah... similar to AvX they are going to need to be able to keep the cosmic entity under control. The fact that it's a bady certainly makes it a bigger problem (though this is comics, so there's probably an 80% chance the baby will start growing at an accelatated rate since that's what often happens to babies in situations like this).