Well, we had 90% tax rates in the 1950s, that mythical time for conservatives when America was the real America, the way things should be and that they’d like to return to. So it couldn’t have been that bad back then. The 1950s did also feature 5-8% yearly GDP growth too so clearly high tax rates didn’t affect economic growth negatively compared with tax rates/GDP gropwth over the last thirty years.
If we put the marginal rate up to 50%, back to where it was under Reagan, we’d get much greater revenues and it would help reduce the deficit. Tax cuts especially since 2000 have been catastrophic for revenues, long term-deficits, national debt etc.