Alternatively, if all those people voted for the candidate they wanted maybe the numbers for third parties wouldn't look so abysmal.
The system is broken since it might as well be 2 parties, but if everyone who would vote for a third party remains apathetic and chooses not to vote at all then it'll just remain broken since those third parties won't ever get anywhere.
If you're going to "throw your vote away" then it might as well be for someone you support.
If more people did this instead of not voting maybe we'd get somewhere.
If there's absolutely no one at all running that you support then by all means, don't vote...though personally I'd rather vote for least terrible. It'd be a shame if the candidate I disagreed with the most won because I decided not to vote.
I'll be honest and you can cough this up to ignorance but I really haven't bothered looking into the third parties. The sad realization though is that it's still a vote of no confidence essentially. I mean I'd vote on principle but not genuinely because I believe in them.
Since this is the case I'd rather not vote for candidates I don't believe in or know about than voting because I should.