They will not be paying half. 52% is the marginal rate, which means that is what your top dollar is taxed at. In no way whatsoever will anybody be paying close to 50 percent of their income. Also, the strive for success is diminished? that is the most bullshit logic I have ever heard. Once you learn how our tax bracket system works you will always have more money if you have more money. There is no way that somebody is going to say: "You know what boss? can you pay 450k instead of 600k this year? I don't want to pay more taxes."
On to your second point. During the 50's Dwight Eisenhower had a top marginal rate of just over ninety percent, and we thrived. While I agree that purchasing things is good, it's not like the government takes the money and puts it in a fire. They use it for stuff. How did you get to school or work today? That's right, a publicly funded road. Did you go to public school? Guess what pays for that. Taxes. We are incurring a huge debt right now, and we can't buy stuff from toys-r-us to get rid of that. The government needs money to function and serve its people like its supposed to.