Still more on inequality

Returning to Tyler Cowen's argument about inequality and well-being, Eduardo writes:

. . .  I, however, think that a marginal increase in well being of the rich is not justifiable unless it -- at a minimum -- affirmatively improves things for those at the bottom.  Finally, depending on the size of the increase for the rich and the poor, the improvement for the rich might not be justifiable, even with a small benefit to the poorest, since the independent harm to social solidarity of added inequality might more than offset a small (absolute) improvment for those at the bottom.

I agree that the "harm to social solidarity" that could accompany increased inequality is a cost that, along with "improvement for those at the bottom," needs to taken into account when we evaluate a proposed policy or the state of affairs.  I disagree, though -- I think -- with the claim that "a marginal increase in the well being of the rich is not justifiale unless it . . . affirmatively improves things for those at the bottom."  One problem with this claim -- it seems to me -- is that it seems to envision "increase[s] in the well being of the rich" as somehow being bestowed from the outside, by some kind of all-seeing-well-being-allocator, rather than by, say, risk-taking, entrepreneurship, and skill.  (I realize, of course, that the rich could increase their material well being in other, less admirable ways, but we don't need to talk about inequality in order to criticize such increases.)  It seems too much to say that "the rich" (who are we talking about, exactly?) are categorically ineligible for what we normally would regard as just returns on investment, effort, and time unless those returns also cause or accompany increases in others' material well-being.