So if I come up with something smart and profitable you should be allowed to copy it without my consent and profit out of it too?
Yes. Why not? If you steal my bicycle, I can't use it anymore. If I steal your idea, you can still use the idea. Only one of us can use the same oven to bake a cake but an infinite number of people can use the same cake recipe.
Economics is rational and common scene.
If that were the case, the last 200 years would look extremely different. Economics is not common sense precisely because people tend to consider only the things they can see but fail to take into account the things they don't see because their idiotic economic polices prevent those things from coming into existence.
If you were a communist you would say exactly the same about the arguments made in the books communists like. And of course you're now thinking "but the difference is that I'm right", just like anybody who's chosen an ideology would.
There's nothing I can say to that. It's like saying that I beat my wife but of course I will deny it because that's what wife-beaters do. It's not a fair argument. Maybe I am delusional, brainwashed or simply mistaken but asserting that it is the case won't convince me of it. You'll have to dig deeper.