Unless you believe in mystical influence, the monk and Mr Buffet have very different abilities to influence others. The monk can't force others to work for his (or her) benefit. Buffet and the rest of his class deprive others of their freedom by dictating how their time is spent - and for whom.

Buffet at least has the decency to occasionally have twinges of conscience about this. Others in his class revel in the contempt they feel for those they inconvenience.

Rawls is arguing against a background where economic theory is the default collective moral standard for society - and his argument is implicitly against the dishonest and false definitions of equality which economic theory promotes and promises.

The fact that other moral systems are possible is an argument for a wider examination of collective economic morality, not an excuse to pretend that personal choices have no influence on others.