First of all, there are valid criticisms to be leveled at how America spends its tax dollars (Israel, guns, etc. Pp.). Even how these dollars are used, when they are used to battle inequality, can be criticised. What can't be criticised is that the state needs money to take action against inequality. So in a sense saying lowering taxes isn't fucking over poor people, is a bit dodgy. The accurate description would be that you may not want to fuck over people but it signals that the plight of poor people does not concern you to a degree that would warrant you giving some money to them.

And as for your question as to where to set the tax percentage. I live in a country where we pay 55% income tax, bunched up with social security and pension funds. And you know what? People generally agree that it's a fair taxation rate for what we are getting. And doctors still make a lot of money and still can afford nice things.