Here is an indisputable fact: either Barack Obama or Mitt Romney will win the presidency on November 6. Here is another: Gary Johnson will not. And one more: far more of those who will vote for Gary Johnson would vote for Mitt Romney than would vote for Barack Obama if Gary Johnson did not exist. Thus, a vote for Gary Johnson indisputably aids the election of the man least desirable to Gary Johnson supporters.
In a world with few certainties, one certainty is that voting for Gary Johnson makes Barack Obama's re-election more likely.
So why on God's green earth would anyone vote for Gary Johnson? I don't ask this to be insulting or demeaning. I truly cannot fathom why, with the known real-world consequences of voting for Johnson, anyone would.
So, given the indisputable, what are the best arguments for voting for Johnson? And the best rebuttals, if what I've written above isn't one of them?