Transcript: https://wearenotsaved.com/2016/08/20/is-it-finally-time-to-start-thinking-about-voting-third-party/ 

There are two reasons to vote. To decide the election and to express a preference. Given that your chances of actually being the deciding vote, particularly in a presidential election are non-existent, you're mostly voting to express your preference, and if one of the third party candidates more closely matches your preference than the two major party candidates you should vote for them.