If you really think someone is evil you shouldn't vote for them. The fact that people do astounds me. However, I do agree with you about voting for a candidate that will move us significantly in the right direction. I have a roughly 75% agree with threshold. That left me with 2 candidates this time!! Otherwise I write people in.
If I was only willing to vote for people who I agree with on 100% of issues I'd have to write myself in every time. That isn't a bad idea really. Or not voting at all might be a good idea as well.