Yeah some people don't get that "property" is just as much a constructed concept as everything else is. It is an agreement/contract between people that is enforced by other people (e.g. the government).

Owning a home might seem more "real" than owning some IP, but it is just an agreement, and without a proper enforcement, anybody could enter and live in your house (which is what actually happens with squatters in some European countries where you're not allowed to kick them out by yourself and police don't care).

So property rights were never "real" (inherently) — they only become real when somebody kicks your ass for violating them. That's the only real thing about it.