Would it be the genetic fallacy to invalidate their evidence because
they are Creationists?
If that is the sole reason for dismissing their argument, then I would say you are guilty of ad hominem. As already pointed out, the genetic fallacy is also known as the fallacy of origins or the fallacy of virtue.
Here is an example of said fallacy:
"Bill claims that 1+1=2. However, my parents brought me up to believe that 1+1=254, so Bill must be wrong."
A logical form
- The origin of the claim is presented.
- Therefore, the claim is true/false.
This type of fallacy typically overlooks the present situation in favour of earlier context. It's also important to note that in some cases, the origin of a claim is relevant to the argument at hand, so an argument of the above form is not always guilty of the genetic fallacy.
For instance, a claim by an expert in their area of expertise is likely to be true.