Since we're talking about presentation, I hope you won't mind a nitpick -- when you say:

The casual reader may be forgiven for coming to the conclusion that these data show that income equality does not makes society poorer across the board - including the poor people it was supposed to help!

(emphasis mine), I think I understand your turn of phrase but it might be preferable to be clearer by leaving out the negation -- the story those little pictures tell is that increased income equality goes with lower income across the board (er, you know, socialism etc...), while, if you want the poor to get (a little bit) less poor, you need income inequality (to motivate the rich who are the only ones who create wealth, blah blah). In other words, the standard trickle-down narrative.