By taking no action at all, you're saying that "I'm morally superior to the candidates, so I'll let less scrupulous people decide." If you truly believe in voting as a tool of moral imperative, then you should do the needful and vote for the most justifiable candidate, regardless of if they're only a little bit less terrible than the next guy.
I understand why the issue is interpreted this way by many candidates, but I believe there are other ways to look at it.
First and foremost, I don't believe in the lesser of two evils argument. The way I see it, I'm being asked how I want to be screwed. I'm not going to dignify the question with a response. I will vote for third party candidates if I actually believe in them. I voted for Nader, knowing that I was "throwing my vote away". For this election, I'm not aware of any that I would support. So I'm left with a range of choices, all of which involve continuing the trend of eroding my rights. I can vote for the person who I believe will erode my rights the least over the course of the next four years, but what about next election? Am I just going to do the same thing? In the long run, the losses are basically the same no matter who I vote for. So what's the point? This has been a continuing trend since before I was old enough to be aware of politics. I think it's absurd that everyone is aware of and unhappy about this long-running trend, and yet I'm encouraged to continue engaging in the exact same course of action that has been producing these exact same results over and over again. If the end result is going to be the same, then I think it's actually more productive to cease explicit support for the repetition of this process. Voting is a form of approval and I refuse to grant approval to my own ongoing exploitation. Quite frankly I don't care if my attitude poses a problem for the system, because the system is not going to change unless it is thrown into crisis.
so I'll let less scrupulous people decide
I find this tidbit especially dangerous, because it implies that voting is the only power that I have and I become powerless by forfeiting my vote. The implications of this are just... painful. The statement doesn't even really make sense, if you think about it. When I vote for someone who I know to be unscrupulous, I am by definition granting that unscrupulous person my approval to make decisions for me in a far more clear cut manner than if I don't vote at all.
But I admit, I DO need to be more involved in my local politics.