Q. Well...? Why does an all-loving, all-merciful God punish people who don't accept him as saviour?
A. That's just it: he doesn't. He leaves us to our own devices: our choices and their naturally painful consequences are their own punishment. God is not like those over-the-top mothers who when their 6 year old comes running home crying inconsolably with a nasty bump on their head from a small accident, proceeds to administer a thorough beating because the boy got that knock doing precisely what the mother had warned him against.
Buddha would say "You are not punished FOR your anger, you're punished BY your anger." Another philosopher would say "Ideas have consequences; bad ideas have bad consequences." Bad consequences naturally cause us pain and suffering. They are not "punishment" per se.
Q. Because to you what is the difference between "punishment" and "bad consequences" per se?
A. There is a NATURAL link between an action and its consequence. Punishment only has an ARTIFICIAL link.
Q. Elaborate please...
A. Penalties or punishments are decided by a person or group of persons: WE decide manslaughter's punishment is death. You don't naturally die yourself because you killed someone; your death is not a consequence of killing someone else. On the other hand, intense pain after breaking a leg or grief after betraying your spouse do follow naturally.
Q. But this "divine" fireman of yours throws you back into the fire if you don't accept him!
A. He doesn't. Like all firemen, when he sticks out his hand to reach you and pull you out, you have to stick your hand out too, allow yourself to be grabbed and hauled out. If you're there fighting and screaming and kicking out as the fireman is reaching out, then he simply can't save you.
That's just how powerful God made us: that we can say no even to Him. Imagine that! As that great African bishop, St. Augustine, would say, "God who made you without you, will not save you without you."
This by the way is also where I disagree with your analogy.
Good day!
18th April 2016