re: economic performance
When the middle class workers are all hired by other middle class workers, then you can talk about how useless the upper income bracket is. Or maybe you don't think capital accumulation and a surplus of investable wealth is important for an economy.
Can we all agree that making sure everyone is allowed to reach their maximum potential is a good idea? And maybe, just maybe, dropping the tax hammer on someone just because they get above a certain income line may not help this process all that much?