But I have to be careful, because I have been known to mix up the Genetic Fallacy and its close cousin, the Fallacy of Composition.
Both Poisoning the Well and the Genetic Fallacy are often used as manipulations in an argument. Watch for them, and call "Foul!" because good reasoning, presentations, ideas and logic are rejected. If something is untrue or invalid, it should be discussed instead of the idea, its origin or its presenter being ridiculed, capice? To me, this stinks of intellectual cowardice.
Even if you cannot exactly identify if the fallacy is Poisoning the Well or the Genetic Fallacy, you will still be able to point out the fact that the other party is not exactly playing fair.
Now I have a bonus for you. Remember Norman the Paranoid Troll? (His response to me giving him that name was to call me "Norman" right back.) Take a look at this: