You'll be surprised by the number of people who thinks if you leave your internet door unlocked then your internet belongings are free to take. There is someone in this very thread arguing that having an internet enable camera in your home turns your home into a public place.
It is also funny, and depressing that many of the same people who think might makes right on the internet ends up lamenting how fucked up life is in their low trust societies, when their mindset is exactly what makes a high trust society — you know, the ones where people don't lock doors — impossible.
Yeah, you might think everyone would realize that there is no technical means to leave your unsupervised door unlocked on the internet. Unlike a physical door, if nobody comes to answer the internet door, it doesn't exist. However, it is impossible for everyone to understand everything.
With that said, the specific someone you refer I am sure has a valid point. When you knock on someone's door and nicely ask for a cup of sugar and whomever is answering the door happily gives it to you, it is reasonable to assume that is something you can take. They would say "no" otherwise.
I get it might be a friend that doesn't fully understand the boundaries of the homeowner answering the door, but it is unrealistic to place the onus on the neighbour looking for a cup of sugar to decide whether or not the occupant is acting in the interests of the homeowner. The fact that the person is already in the home to be able to answer the door implies that there is trust in that person to do right by the home.
By the same token, if the homeowner found out about the cup of sugar that they didn't want given away, most people would address it with the friend to see that it doesn't happen again, not go on a rampage with the neighbour. It is well understood that anyone within the home saying "yes" is to be considered authoritative. It is the only reasonable way.
It is also funny, and depressing that many of the same people who think might makes right on the internet ends up lamenting how fucked up life is in their low trust societies, when their mindset is exactly what makes a high trust society — you know, the ones where people don't lock doors — impossible.