Part of my problem is that a lot of justification for voting Democratis that they are the lesser of two evils. that should not make voting Democrat the right thing to do. if two options are unethical, as I believe voting for either party is, it does not make the lesser of these two somehow ok. if your options are kill an infant or kill an adult, you are still a murderer, and a convincing argument could be made for either option.
It's true, and I also know a lot of old-school conservatives who believe every living Republican is basically a libertarian and that the last real conservatives died in the 19th century. I don't know if they vote, but if they do they're inverting the paradigm and making the best of a bad situation by voting Republican. Goes both ways. However, that's not a full justification for abstention -- the more powerful argument, in my opinion, is that past a very localized point, an individual's vote simply doesn't matter. Mathematically, systemically, etc. In the situation you outline, if my vote mattered I could still express my value scale (assuming one candidate was even slightly less bad than the other). Unfortunately, under the current system that won't help my vote count.