Property can never be theft as theft only exists if property exist. You can't steal something if no one can "own" anything.
> what gives you the right to compel me to defend your property?
No one has a right to compel you to do anything.
However, you will act in your best interest. How about I pay you to defend my property?
Or, perhaps it is in both of our interests if we defend each others property. After all, if you let others steal my property, yours will probably be next.
This holds even more true for rights.