If a rich person invests in a business, either directly or through stock purchases, it means business can grow and hire more people.
The real reason to oppose increasing tax rates on the wealthy is that it's a good bet they could do more to help the economy if they keep their money rather than have their earnings confiscated by the government and spent on another round of stimulus.
Driving with one foot on the accelerator and the other on the brake is likely to get you nowhere, but certainly will burn out vital parts of your car. Similarly, cutting taxes on the middle class, but increasing them on the 'rich' is likely to result in an economic burnout.
But only 'rich' people by definition have the 'extra' money to buy things and invest to create economic growth. Do we really want to tax that 'extra' money away - and give it to the government to spend? Does that make any economic sense outside of politics and our emotional desire to make everyone suffer equally through these tough times?