Glad to see Shua's still out there, fightin'.
In my experience there's a huge amount of variation in what even many very educated people will tell you about the ethics of voting when you ask them why it's important to vote and how you should select a candidate. Many of them jump straight to the shockingly and transparently weak "deciding vote" argument.
Yes, that's a really stupid argument. I vote because it makes me feel good, not because it would be rational. And this is the case for most people, really. They only don't know or admit it.
Well, sure, but really it's just about the basic fact that aggregates matter. I've voted for some right crooks in my time (granted with a transferable vote it's a whole different issue, but still).