My first comment is a bit snarky and for that I apologize. Not quite sure how that warranted such a vitriolic response. I even explicitly stated I was not arguing that capital gains should be taxed the same as earned income, just didn't see the need for the disparity to be increased.
If tax structure has nothing ("jack shit") to do with raising the income of one group over another it would make no sense for some groups to spend so much money lobbying congress on modifying the tax structure.
Your proposal of a flat tax would certainly get rid of some gaming of the system (see lobbying above). Unfortunately, given our current human nature, I do not see a pristine tax policy lasting a single Congressional session before the first "oh, well except this" gets thrown into the mix. Seems like every tax simplification scheme has been but a temporary reprieve from the inevitable trend.