Tax on big banks?

Obama is pushing for a tax on the fifty biggest banks on the country. The banks are wailing, Republicans are opposing, but actually, it's not a bad idea in my book. The fifty big Wall St banks bear a lot of responsibility for Great Depression 2.0. The "too-big-to-fail" banks made risky loans on the theory that when they pay off, you get rich, when they don't pay off, the taxpayer (ME!) bails you out.
Since the too-big-to-fail banks enjoy taxpayer support, they might as well pay for it. If they find the tax too heavy, they can always spin off parts and become smaller. Which is a fine idea. That makes them small enough to fail. Which is good, they will be more careful.
Plus, the big Wall St banks don't do a thing for me. They don't do car loans, they don't do mortgages, they don't lend to companies, they don't do venture capital. Far as I can see they just do deals with each other. So tax the bejeezus out of them.