Is this a logical fallacy? If So what is it called?

Hello,
I was wondering what kind of fallacy is it when Person A cites historical events to support an argument and then person B, instead of speaking about how that historical evidence is fallacious (False equivalence, biased sample, ..), they instead attack the credibility of that event or of its source and dismiss it as therefore not being accurate.
Thanks.

I'll add to Dr. Bennett's response. Attacking the credibility of a source is ad hominem argument. People often use this to divert attention from the issue.

However, it is legitimate to question a source's qualification or track record. Who do you believe on medical issues? A Facebook source says that vaccines are dangerous. Yet a physician says that vaccines are safe. It is legitimate to say that the Facebook source is less reliable than the physician. Climate change: many people believe what they hear from unqualified people on cable new or talk radio, instead of paying attention to scientists. So it is legitimate to question a source, but it is important to do so rationally.

Questioning the credibility of the event as well as the source is perfectly legitimate, however, the conclusion should be that is unlikely accurate, rather than it is not accurate. For example:

Person 1: A hundred years ago, a guy named "Frank" wrote down that he witnessed a unicorn pooping rainbows.
Person 2: I find that very difficult to believe based on the extraordinary nature of the claim and the historical source (some guy named "Frank").

However,

Person 1: On September 11, 2001, two planes flew into the World Trade Center and both towers collapsed.
Person 2: I find that very difficult to believe based on the extraordinary nature of the claim and the historical source (virtually every media outlet in the world).

is a different situation. Not fallacious still, but person #2 is displaying an unreasonable level of skepticism (not scientific skepticism) that is best described as denialism .

It must be an error in reasoning not a factual error.
It must be commonly applied to an argument either in the form of the argument or in the interpretation of the argument.
It must be deceptive in that it often fools the average adult.

Questioning the historical veracity of an event is not an error in reasoning unless the basis of rejection or acceptance is solely based on the age of the event. (See Dr. Bo's Pseudo-logical fallacies, Chronological snobbery:

Chronological Snobbery: Thinking, art, or science of an earlier time is inherently inferior (or factual) when compared to that of the present. This is more of bias, and when used in argument form, is covered by the appeal to novelty or argument from age.

Person A: 2000 years ago Jesus died on a cross for our sins.
Person B: There is no proof of a historical Jesus and there were no eyewitnesses.
Person A: We know Christianity is at least 2000 years old, so it must be true.


Needless to say, feel free to poke holes in this