2 choices, one pure flaiming shit, or one slightly less shitty =/= choice.
Even if I accept your characterization, you're still describing a clear choice. Why should I do anything that would increase the chances of "pure flaming shit" to win over "less shitty"?
Barring some unforeseen and absolutely unprecedented event, the only possible outcomes are that either Romney or Obama will win in November. ANY choice we make (staying home, voting third party, etc.) can only play into one of those two scenarios.
If we're dissatisfied with the choice (as I am too, to some extent), I think the place to fight is in the primaries, state and local elections, off-year elections, etc. Building up the progressive wing of the Democratic party (or resuscitating the "moderate/liberal" wing of the GOP) might make the choices more palatable in the future.
Also, despite Obama's failings, I think it's an outrageous false equivalency to claim that he and Romney are nearly the same. The oil companies, hedge fund managers, and modern-day robber barons like the Koch brothers and Sheldon Adelson certainly don't think so. One side wants to blatantly transfer more of the nation's wealth to a small elite, the other wants to at least retard the process slightly. One side may disappoint unions now and then, the other wants to utterly exterminate them. One side at least passed a flawed effort to expand access to health care, the other will be completely beholden to the insurance companies and for-profit providers. One side may be lukewarm towards marriage equality and reproductive rights, the other wants to amend the Constitution to ban them! And this list can go on...