This smuggles in so many assumptions and misconceptions I find it hard to decide where to start. Maybe from the beginning:

> The pope, as a Christian, is well aware that human nature is fundamentally sinful.

This might be true in the context of the original sin, but philosophically speaking you can't make this assertion, since there is no consensus on what the human nature is, or even if there is an essential human nature.

> If you take away the ability for people to profit themselves from their work, they just stop working

That's incorrect because it assumes the only reason for working is profit, in which case art for instance in many forms wouldn't exist.

> they just stop working and you get mass starvation like China and Russia post communist revolution

This is just a wrong impression what communism is. What creates these conditions are autocracies and oligarchies, not communism. In either case, even if this were true, this statement isn't falsifiable so can't really be taken into account.