Not the OP, but I think a lot more people nowadays should read (or re-read) Locke's "Two Treatises of Government". That book is famous mostly for the second part, where Locke actually intellectually imposes private property as a thing in the Western world, but I found the first part equally interesting, where Locke fights against a guy called Filmer, who was of the opinion (prevalent until then) that all property was rightfully owned by the King, transferred to him from generations past since Adam.
The thing I'm trying to say is that yes, private property is just a social construct, there's no divine nor moral thing about it, the concept came alive (so to speak) only because some guys in England didn't like that their possessions were in danger of being confiscated by the King's men.
In the end private property is indeed theft, more exactly the imposition of someone's moral values over the other's by intrinsic force (if you "steal" you might go to prison or worst). The sooner we realize this the better, there's no second-guessing about it.