There are many definitions of theft – different societies have different laws governing control over objects and resources. This control is basically how property is defined. Different kinds of laws mean different concepts of property. Some wealthy property owners, when confronted with the possibility that the (more numerous) poor may vote for higher taxes on the wealthy, will argue that taxation is theft. Other less wealthy people, particularly those who work under someone else, may believe exploitation is theft. Then there’s Proudhon’s famous declaration that, “Property is theft.”
The following are reactions to the concept of conquest from two different types of pro-capitalists.
Ownership Through Conquest is Justified
This view claims that conquest is justified because the conqueror risked his life (or at least risked the lives of his minions) in battle, and thus has earned the right to control.
However, these pro-capitalists are opposed to the concept of an anti-capitalist revolution, claiming that would be a violation of their property rights. If employees “conquer” their places of work by escorting their boss off company premises, these pro-capitalists do not see that as a “legitimate” form of conquest.
Ownership Through Conquest is Not Justified
Other pro-capitalists do not believe conquest is justified and yet they oppose returning conquered land and resources to the natives (or their descendents). They believe conquest is an injustice, but do not have a good idea of how to rectify that injustice.
Conquest results in wealth for the conquerors. Then that wealth is distributed to cronies and offspring. On and on it goes - not just in this country, but around the world. If you trace back the history of ownership of land and resources, how much of it doesn't originate in conquest (or what some would call theft)?
How far back do you have to go before you consider property valid? If one group of Australopithecus or Cro-Magnon conquered land from another group of Australopithecus or Cro-Magnon, do their ancestors have to return it? If not, why not? Is there a "statute of limitations"? If so, how many years does it have to be, and who decides on this number?
Why Have Society?
Personally, I don't (that's right, don't) support giving back everything to the natives (or their descendants). Instead, I assert that the resources be used for the benefit of everyone in that area, whether it's later settlers, recent immigrants, the natives, whatever. Human beings form societies in order to protect themselves. The point of the political, economic, and religious systems they set up is to benefit as many of the individuals in the population as possible. Because property requires society to enforce it, why should society enforce something that is not beneficial to it? It is not an "axiomatic" right - if it has become perverted to the point at which it is judged no longer beneficial, then it (or at least parts of it) should be dispensed with - especially if it is causing the death of others.