This is largely a myth due to the fact that the wealthy pay virtually all of the income taxes anyway (top 20% pay 87% of the income taxes) and the poor and lower-middle earners pay nothing or less than nothing (45% of households in 2015). As a result, tax cuts will always necessarily "favor" the wealthy, since you can't cut income taxes for people who don't pay income taxes. Essentially, the growth in income inequality has enabled the rich to pay an increasing share of the income taxes despite decreasing top tax rates (note: due to rising incomes, that doesn't necessarily even mean the rates they pay have decreased, since more income means more paid in the higher tax brackets). The share paid by the top 20% has increased to that 87% from 57% in 1969 and 69% in 2005.
This "inequality" isn't talked about much by the media, but presents a serious political/social danger in my opinion.
http://www.marketwatch.com/story/45-of-americans-pay-no-federal-income-tax-2016-02-24
http://www.nbcnews.com/id/29861648/...ll/t/how-tax-burden-has-changed/#.V-O4DPkrK00