I like to give this example to illustrate the point. Suppose a man is walking across a desert, dying of thirst, and sees me carrying two water bottles; I only need 1 for myself. I offer him another one for $10,000 which he happens to have on the only item he carries with him: his debit card.
Under conventional collectivistic morality, I am committing a high moral crime: I am enriching myself by "exploiting" someone under the duress. But this fails to account for the simple fact: that if I had not been there at all, the man would be worse off: he would die. Is living, but having $10,000 less, better than dying? Well, if the man accepts my offer, then he certainly thinks so.
Therefore, the only way to make this moral framework work - and consistently so - is to not only demand that I give the man a water bottle for free (or at a very low price), but demand that I actively scout the desert and look for people like him. My life must, to some extent, be a hostage to the needs of thirsty desert wanderers. Needless to say, this is a bleak world to live in.
Yet this is exactly the world nationalists, socialists, Christians, Muslims and other collectivists see themselves living in. They all believe that there is a claim to their time and resources coming from outside of them. That without serving someone else or something else actively, they are unworthy of living. They differ in who they believe to be that external source, but they all agree that their own preferences and desires are secondary to that mystical duty to the source.
This makes lives of various manipulators such as kings and archbishops very easy, and everyone else's lives needlessly hard. But the manipulators are much more proactive with instilling this deformed system of values in everyone, so they end up winning the public discourse.