The entity making the tax code (the government) and the entity that collects taxes (the government) are one in the same. If the government wants me, as an individual or business, to pay taxes at a certain rate X, they should write the tax code so that I need to pay taxes at X%.
I don't think it's anyone's moral responsibility to pay a certain percentage in taxes. From a moral perspective, people have different ideas about what percentage they should pay. If I'm a small business owner, I might believe that my contribution of providing employment to 50 people is enough, without having any moral obligation to pay taxes on top of that.
Or, I could be a hugely wealthy investment banker. I make $1mil a year. But I don't feel morally obligated to pay 30% in taxes because every year I give $300,000 dollars to charity instead. Or this one time I made a $500,000 endowment for the arts.
Taxes and morals are too separate to be linked so easily.