I agree that it's an arbitrary social concept, but it's not ridiculous at all, deeper thought or not. I think it's completely reasonable to expect that my house is my house, and others aren't allowed to enter it or live on my property without my consent. If you think we all should live commune-style and have no property or physical privacy, that's certainly fair for you to believe, but the vast majority of the people in the world would staunchly disagree with you... hence the concept of property ownership.

Certainly there are issues with how we've implemented property ownership, but I don't think the concept itself is inherently flawed or ridiculous.