I think the point is not that it's taking money from the rich. I mean, that's a necessary part of it. The point is that that money is forced to recirculate in the system.
The thing people seem to forget is that taxed money doesn't just disappear. It right back into the economy. The target, predominately, is the working class, either directly via Gov't employee wages, or social programs. Or it goes back indirectly, through Gov't contractors. At which point it filters back up the system to the rich.
The rich do not usually sit with cash in their bank account, and even if they do the system is built to keep that money recirculating. Banks use fractional reserve lending to take those deposits and lend them out several times forward. Otherwise the money gets invested in companies from your large caps, small caps, VC, to angel funding, etc...
Basically there is no such thing as stagnant money imho.
What taxes imply (again in my opinion) is that we believe the government is better at investing that money than the economy participants themselves. In some cases that is true where the return is over several decades or there is little to no direct monetary return at all (but still very necessary - social programs). But in many cases it is not.
The thing people seem to forget is that taxed money doesn't just disappear. It right back into the economy. The target, predominately, is the working class, either directly via Gov't employee wages, or social programs. Or it goes back indirectly, through Gov't contractors. At which point it filters back up the system to the rich.