Well they live by the myth that the rich are job creators, while dismissing supply-and-demand/real capitalism.
I dont doubt that some
of the rich entrepreneurs are job creators and as such deliver more tax revenue to the government than just sticking that money into a bank, however in times of recession an entrepreneur will be as cautious as everyone else, but with more money. They will want to be damned sure that their enterprise will be a success before putting their money on the line, but that is exactly what the banks are doing as well, which is why the US and the UK governments are both perusing QE, to (in theory) encourage banks lending to individuals and small businesses by freeing up capital.
The big problem with all of this is that of confidence (or fear, take your pick) in the economy as a whole, and in more modern times regional economies and the entire world economy.
None of these issues will be affected a lot by reducing the tax to the riches people in society (or by not increasing it to the same degree as other tax payers), so Romney's tax system is heavily flawed IMO.
There are 2 other significant issues surrounding the question of taxes and the rich, both of which have been proven repeatedly in history. If a government taxes the rich "too much" the government will actually receive less
in tax than if the tax rate was lower (I cant be bothered to look it up now), but there was a Labour UK government that did this and ended up with a tax rate for the rich that was around 80%, the government actually received significantly less revenue than when the tax rate for the rich was at 40%. The other thing is "tax loopholes", the irony is that you have to be rich to afford to use these loopholes, which is why one of the big reasons why rich people often pay a lower amount of tax than less well off people.
I certainly would not suggest that trying to taxing the rich into poverty out of a warped ideology is a good or sensible idea, because they will likely just move to another country with all of their money, you want them to stay put and pay their taxes to your country (unlike what France it trying to do with an 80% tax on the mega rich, please move to the UK and start up businesses here). A sensible government will pick a tax system that is not just fair and progressive, but actually gathers the largest amount of tax revenue, exactly what that is will vary a great deal from one country to the next. Finally, tax loopholes need to be closed, and companies (or individuals) that use offshore tax havens rather than paying taxes in the country the operate in need to be forced to pay taxes in some way in the country that they operate in.