What if I’m dying of thirst. Don’t I have the right to shoot him so that he doesn’t drink my water and cause me to die of thirst if he persists in trying to steal it? If I have the right to stop him, I have the right to stop him in all situations. Rights aren’t contextual. If you ever make rights contextual, you defeat the purpose of having them, and thus you defeat the purpose of the system. Of course I can share the water, or even sell it to him at a price we agree on. But if we don’t agree on the price, he doesn’t get to take it from me.