5% owning everything is the nature and goal of any capital dominated economy by the end. Capital builds yet more capital, thats the nature of the system. Without getting extremely long winded into economic theory unless you want it you can always do some studying on it yourself.
Modern government does aid this behavior, on that we agree. But again this is the nature of the beast in a capital dominated structure. Its not always the "more you get away with" though it is at times, but its the more you CAN enable or simply accomplish. The capital allows you these opportunity's. As capital accumulation takes place and concentration builds it in turns enables more growth and more accumulation. Look at corporate mergers, buyouts as examples that are readily understandable. This is not limited to the business sector either, it occurs in the private sector also.
Im not sure you understand a flat tax or a scaling tax. A true flat tax is exactly that, flat across all social strata. Be it 5% or 45% it the same if you make $50 or $5 Million. The issue i stated earlier is that a flat rate high enough to "Make the rich pull their weight" is going to be MASSIVE to anybody less income oriented than them.
45% of $5 Million is $2,250,000
45% of $50k is going to be $22,500
45% of $50 is $22.50
The math is ultimately destructive to the lower classes -and- middle class when levied in a way to "make the rich pull their weight" yet if lowered to 5% or so becomes a PITTANCE to the capital rich. Thus the normal solution is a sliding scale income based tax. Our current tax system IS BROKEN, i will not argue that you are correct.
Lower tax rates spur growth by encouraging business immigration and hiring. Higher taxes can have the opposite effect BUT causation is not correlation, different economic factors can effect matters in vastly and wildly ways. This whole subject itself has books written about it.
I did by refuting your logic. Why is it illegal? Show me how a law is being broken by tax collection and you have an argument, but without that you have theory craft. Im sorry I do not agree with current tax practices wither, I despise them in many ways but fair is fair to both sides at it is -now- constitutionally legal. Changing it is an admirable goal, but rallying around a false premise leads ultimately to defeat.
No argument on the interest point.
To end with, I have an interesting "Capital economics" video 101 you might enjoy, and I bet you might agree with much of it (and not so much other parts, but such is the nature of economics!). Its nicely drawn to go along with a lecture given just this year by David Harvey. I dont agree with parts myself but it is nothingless a good watch and can aid when I refer to capital accumulation.
YouTube - RSA Animate - Crises of Capitalism
Good night.