Fact: the Laffer Curve exists. When taxes are cut significantly to have an effect (i.e. the 1920s, the early 1960s, the 1980s and 2003), economic booms result.
Fact: a rich person facing heavier taxes won't work as hard, meaning less tax revenue than expected. If you scroll down through this, you'll see my explanation that the 1990 tax hike failed to achieve its stated objective of balancing the federal budget. Clinton's 1993 tax hike also failed, as Don Luskin explained:
As you can see, from 1993 (the first year of the Clinton tax hike) to 1996 the increase in revenue is somewhere between negative and negligable -- the increased revenues Clinton hoped for from his tax hike simply did not materialize. The positive surprise versus expectations started in 1997 and the years after. What happened in 1997? A Republican congress cut the capital gains tax. So it all went just perfectly according to supply-side theory.And federal spending didn't exactly go down, either. The budget deficit was reduced more because of increased tax revenues than any sort of "fiscal responsibility."
Fact: a rich person taxed more will have less money to spend (on goods and services that other people produce, almost always people of far lower incomes). This means lost jobs. A rich person taxed more will have less money to save, meaning less money for businesses to borrow, meaning reduced business expansion. This also means lost jobs. Also, higher taxes on the rich means less money available for the rest of us to borrow in the form of mortgages/home equity loans, auto loans, even credit card and store debt. Interest rates will therefore go up, meaning "the poor" won't be able to afford loans they previously could, or the Fed will pump more money into the economy, causing inflation that hurts "the poor" the most.
Do liberals honestly think it's better to have high taxes so that a government bureaucrat can make a cut for himself, waste some more on "overhead," and return pennies on the dollar to you? They must, because no matter how benevolent the purpose behind their beloved "social spending," that is the inevitable result. It's like forcing someone in an apartment building to keep his front door open, so that heat can flow out and into the open apartment of his neighbor across the way. Yeah, it'll work a little, but not as well as the other neighbor getting his own source of heat. Who actually thinks the neighbor with heat will want to keep his running as strongly, knowing so much is going to waste?
To make another analogy, I don't know about the rest of you, but I'd rather get out there and earn my wages honestly so that I can earn entire loaves, instead of relying on government to seize others' loaves but give me only breadcrumbs.