Capitalism (private ownership and operation of property) in a free market system (system free of government intervention)
There is no such thing as private property without government intervention. "Property" in any sense more than what a nomadic human could carry with them, is a government creation. To "own" something means exactly and only to be able to call on government force to obtain or maintain control of that thing, or to be free from the usual government sanctions for such use of force. Land ownership is rooted in government-issues pieces of paper. Every physical good ultimately comes out of the land. So-called "intellectual property" is entirely made up by the state.
Property is not a right, it is a human invention that at best we can use protect rights -- or at worst can use to protect the power of a ruling class. Capitalism is a system where the state the notion of uses property to preserve the power of a small artistocatic owning class.
Anything that reduces individual freedoms is less moral than anything that increases individual freedoms.
And capitalism reduces individual freedoms, and is thus immoral. QED.