Another version of ad hominem attempts to impugn someone's
objectivity by claiming that he or she has a vested interest in the view
he or she defends.
This tactic is sometimes called "poisoning the well", and it is
obviously fallacious. The fact that someone might have a
nonrational motive for supporting a position does not mean the
position is false, and it certainly does not mean we can decide
ahead of time that all of his or her arguments for the position can be