Why are Republicans so Upset About Poor People's Taxes?

From Ezra Klein -- why are Republicans so upset about poor people's taxes:

Democrats are making Americans angry with poll-tested language arguing that the rich don't pay enough, so Republicans are responding with an argument that the poor are mooching off the middle class. Then there's the underlying ideological framework: Republicans believe, either implicitly or explicitly, that the economy is really driven by well-compensated, wildly productive geniuses at the top, and so the true aim of tax policy is keeping their tax burden low so they have sufficient encouragement to unleash their potential. Democrats believe those folks have so much money that they're no longer primarily driven by monetary concerns and that, either way, the key question for the economy is how to get more demand into it quickly, and for that, tax cuts to the poor are clearly superior, as the poor spend the money they get.

Link is here: http://www.washingtonpost.com/blogs/ezra-klein/?wpisrc=nl_wonk