As I noted, sales taxes are among the most regressive forms of taxation, and I personally think that they should be replaced with more progressive forms of revenue, like income, or preferably, wealth taxes.
This isn't true, sales taxes are not perticularly regressive. And most economists will tell you that, moral questions aside, they're probably the best way to do taxes.
In America, the most regressive taxes are Social Security and Medicare. That's because wealthy people tend to live longer; while young black men (unfortunately) live much shorter (because they're far
more likely to be murdered, what with gang violence, drug culture, etc.; note that I'm not saying this is inherent to being black, but it's the result of the situation they find themselves stuck in). The result is that SS is significantly a machine for transferring money from young black men to rich old white ladies. THAT is regressive.
And many common deductions, particularly on mortgage interest, are regressive. And egregiously so, because they're forcing people who can't afford to buy a house to make up the difference from the people who were lucky enough to get to that level.
So SS is entirely regressive. A standard tax fee for all people (say, $X,000 per person) is regression-neutral: everyone has to pay exactly the same amount, so it's neither regressive nor progressive. A flat income tax (e.g., 11% of your income) is progressive, because those making more money have to pay more money. Our marginally-increasing income tax you might think of as being doubly-progressive, because its progressive scales up super-linearly.
By way of comparison, Ben Franklin's idea was that rich people should pay more, because it's the job of the government to protect ourselves and our property; so if you've got more property, you're getting more of the government's services, thus you should pay more. So if you make twice as much, you should pay twice as much. But that's a FLAT tax rate, not America's current system of marginally-increasing rates.
Sales taxes are not regressive in this way, because they don't get lower for richer people. If you're picturing an ostentatious millionaire living off the backs of the poor, that's not accurate. That rich guy is going to be buying all sorts of fancy cars, expensive wine, etc., that the poor can't even afford. And he's paying the sales tax on that.
The good thing here is that there's a loophole to the sales tax: just don't spend the money, but invest it instead. And the thing about saving is that it's actually an investment: your savings will be turned into the money for someone else's mortgage, or paying to start up a new business, or to invest in newer more efficient equipment for an exist business or something like that. And all those investments are helping other people achieve their own goals, creating jobs, etc.
The end effect of taxes is that when you tax something, you wind up having less of it (and conversely, removing the tax will generally result in greater demand for it). The governments understand this, and frequently use this fact intentionally, such as increases in cigarette taxes to get people to quit smoking.
This is why income tax is a bad thing. We don't want to discourage people from making an income (i.e., working): we want to encourage them to work, to produce more. But at the margins, there are people saying "it's not worth me working any more time, because the amount I will make after taxes isn't going to pay for my childcare" or something like that. And that decreases total productivity.
A "wealth tax" is essentially the same thing, since wealth is just the accumulation of income over time. And the way to avoid that wealth tax would be to spend more -- and just as with a sales tax, we don't want to be encouraging the commercial, consumerist economy.
We want people to buy what they need to achieve their own ends, and to save (i.e., invest) the rest in order to enable the rest of society to pursue their dreams.
EDIT: added some clarifications