One of the primary purposes is to shut down the existence of HFT as we have established that it is parasitical - at least, my arguments as to why it is parasitical have yet to be countered based on anything derived from the tangible universe in which we live, but I eagerly await any angle on this which I have yet to consider. There are a few ways I interpret the latter part of your post: that the big HFT banks would be able to continue with HFT? Or that big non-HFT operations would simply squeeze the little guys out of the market?
Big non-HFT operations would continue. They wouldn't squeeze little people out of the market, the tax would do that for them. What would be left of the little people would be buy and holders, now getting severely raped by markets controlled only by big money, because retail traders would be no more.
We do not disagree on HFT and we do not disagree on the need to get our economy back to reality, or at least more distant from money making money. We don't even disagree on the potential usefulness of this tax... but why can't there be an exception for retail traders? You keep overlooking this point.
Additionally, while I hate the financial services industry as much as you do, we both acknowledge that it IS a large part of the economy. This tax would decimate it, and what becomes of all the millions of people that work in that industry? The tax will make them jobless overnight, but there won't suddenly be a glut of manufacturing jobs for them to jump into in the same time frame.