"...Hope for the best, but prepare for whatever you can think of. That way, if something does turn out for the worse, you'll have a chance of being able to do something about it."

That isn't to say he doesn't agree with the tailed boy's assessment of the first option being the more likely, even if not from quite the same angle of reasoning. It's more that the thought has occurred to him that, with it being possible to control such an entity, someone might get the idea to try.