I have to see the context of this scene in the episode. I do think Rumpel has a hard time loving anyone besides Belle and Bae. Even then, he has trouble understanding what it means to love, to trust, to sacrifice. When it comes to Henry, even if there were not a prophecy haunting them, he might not be ready to love the kid just because of the blood tie, and more importantly to Rumpel, believe that the boy loves him. Of course, in this Rumpel might be a blind idiot, because if Henry can have love for Regina, he ought to realize Henry could love him too. And if he does know that, or feel that, and still wants to hurt Henry, THEN I agree, he reaches that point where it will be really hard to redeem him. We don’t know enough yet though to see what the writers have in store.
Maybe Emma’s magic is sort of pre-paid or else the cost of magic that comes from dark emotions is heavier.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass