Your are mythtaken, pun intended.  

Actions have consequences as demonstrated by the third party candidacy of H. Ross Perot delivering the White House to William Jefferson Clinton in 1992 and 1996.

In your alternate universe where voting for third party candidates has no impact, doing so is equivalent to loss of bladder control whist wearing dark slacks.  It makes you feel nice and warm for a few moments and no one notices. Surely there are better avenue to follow in pursuit of self gratification.