Supply side economics (another name for "consumer spending") only works IF you don't have any disruptions to the economy. You can use "the multiplier affect" (taxing the greater volume of consumer spenders which generally equates to taxing working- and middle-class Americans) to great affect and, thus, leave the wealth-class alone since they have the greater share of disposable income AND tend to be the larger instruments of business creation and free market investments. But all that is assuming there is no disruption to the economy. If such a disruption does occur, i.e., the housing bubble, the banking collapse, a global pandemic, a significant reduction in global oil supply, a major war, etc., etc., where corporate America (i.e., the "wealth-class") can't inject money into the (investment) free market, banks can't lend, consumers lose their jobs and, thus, have no income to buy things using cash nor credit, what keeps our economy moving?
Think about it...