Absolutely not. Especially if you live in an area that is heavily blue or red voting for a third-party candidate gives you a much louder voice. Because I lived in Arkansas I knew all the electoral votes would go to the republicans (in 2012) I voted for Jill Stein. It's only true that third parties couldn't defeat the lesser of two evils because we believe it to be true. If we have enough people change their minds about that silly belief the reality will be revealed. To be on the ballot third parties need at least a small percentage of votes and to attract third party voters the major parties are likely to adopt policies supported by third parties if they get enough votes.

Donald Trump is clearly more of a threat to humanity! Do you really think he could possibly be a more reasonable choice than Hillary or Jill?
Personally I think she was a great secretary of state.