Politicians have long used the tax code to manipulate us. Mortgage deductions steer us to buy bigger houses, and solar tax credits persuade us to put solar panels on our roofs. The tax code also steers us toward certain forms of giving back, and toward particular healthcare decisions. But every time tax rules nudge us in a chosen direction, they preempt the market's signals, John Stossel argues. America suffers when government turns taxes into a manipulative maze.