Except that's ad hominem fallacy
Uh, no. Ad hominem is when you attack the person who wrote it, whether that be their previous history, or their personality, in order to call their argument invalid.
You might be thinking of the Genetic fallacy, which is where you dismiss a piece of information based off of where it came from. Note that you have to be careful when crying out "Genetic fallacy!"; as sometimes you can validly dismiss information that comes from especially unreliable sources.