What is the problem with having both progressive and regressive taxes?

Then you should like socialism. In our nation everyone is suppose to be subjected to the same laws, rules, regulations and taxes. It is not fair to punish any one group of people simply because they make more money than another group. This is no different than saying asians should pay more in taxes than whites and whites more than blacks and blacks more than hispanics. If someone goes to a grocery store to buy a gallon of milk the gallon is the same price regardless of how much you make. Wouldn't it be ridiculous to have one person go to a store and buy a gallon of milk for $2 because their income is "x" and another person have to pay $100 for the same gallon of milk because their income is "y"? Our government taxes too much & spends too much. We need to dramatically cut taxation and reform the tax system so that it is based on fees and sales taxes and not property & income taxes. I'm talking both state & federal levels.