This statement is not supported by the facts.
In 2007 the top 1% of earners paid over 40% of all Federal income tax. The top 5% of earners paid over 60%. In fact, income taxes are always diproportionately paid by the highest earners; and the disproportionality has been steadily increasing.
Bush’s cuts in lower-middle-class tax rates was one of the several incredibly stupid things that he did. In pursuit of a goal that could never be achieved en masse (making people earning $20,000-$50,000 a year feel a common cause with entrepreneurs and executives) he instead inflicted an injury the depth of which we are only now beginning to feel: making people earning $20,000-$50,000 feel that the government services are on a net basis, given to them and not paid for by them.