Tyler, responding to Karl Smith, responding to Steve Landsburg, asks:

[I]f government action to redistribute income is morally required, in the
meantime is not greater private charity morally required too?

Tyler’s not impressed with Karl’s position.  Karl:

If we want to be truly honest then most people mean something like
this: I would prefer a world in which all other rich people paid more
taxes and I paid less. However, I doubt that anyone is going to go for
this. So I am willing to settle for a world in which all rich people
including me pay more in taxes. I am not willing to settle for a world
where I am the only rich person paying more in taxes.

My challenge for Karl: What moral position, if any, would actually morally justify your preference? 

Most deontological moral theories say that government enforcement and moral obligation have nothing to do with each other.  If you’re obligated to help the poor, you should fulfill your obligation even if the government looks the other way. 

Most consequentialist moral theories say the same.  If taxing you more to help the poor raises social utility, then your voluntary gift to the poor will presumably have the same effect.

The simplest moral theory I can imagine that would justify Karl’s position says: (a) you’re morally obligated to obey the law, (b) morally obligated to support utility-maximizing laws, but (c) not morally obligated to unilaterally maximize utility.  But just imagine making a populist protest sign consistent with this position.  An egalitarian who defers to the law, does cost-benefit policy analysis, and refuses to go above and beyond the call of duty has become everything he hates.