Poisoning the Well – an argument against another person that is delivered in such an emotionally biased way that the victim’s response looks inherently dishonest or immoral.
 

This tactic works as a distraction from the real issue, but the speakers of this fallacy often do not know that they are expressing themselves in such an emotionally biased manner.  Poisoning the well often may involve personal attacks, loaded language, equivocation, distortion, or other fallacious appeals to emotion.
 

EXAMPLE

A high-strung store owner accuses a teenager: “Of course this liar will tell you he didn’t steal my stuff.  You can’t believe a thief.  Go ahead – ask him.  He’ll just deny it!”

How is the accused supposed to respond to these accusations?  No matter what direction the respondent takes, his answer is tainted — poisoned — by the accuser, which reduces the victim’s credibility (his ability to be believed).  Before this man can even defend himself, he has already been publicly judged guilty.  His response will look suspicious because his jury has already turned against him.
 

Often, poisoning the well preys upon people’s stereotypes and fears.  During the days of slavery, African Americans were often found guilty simply because their skin color worked against them in a world dominated by white men.  Blacks who were accused of crimes were most likely found guilty, even if a hundred witnesses knew that the white men were truly to blame.  Harper Lee’s novel To Kill a Mockingbird illustrated this type of situation quite well.