Final answer:
The fallacy presented is a combination of a fallacy of diversion and an ad hominem attack, commonly known as a genetic fallacy. It dismisses an argument based on its source rather than its merit.
Step-by-step explanation:
The statement "You can't believe that! That's the kind of stuff you hear on Fox." is an example of a fallacy of diversion and an ad hominem attack. It attempts to discredit the claim not by engaging with the actual argument or evidence presented, but by attacking the source, implying that anything from that source is inherently untrustworthy. It's also a genetic fallacy, which judges the merit of a belief, claim, or argument based on its origin rather than its substance.
This kind of reasoning is flawed because it does not address whether the information is true or false; instead, it suggests that the source itself automatically invalidates the content, which is not a justified assumption. One should evaluate the actual evidence or argument rather than dismissing it based on where it comes from.