Did you see the skit?
Yes, and the reporter made several fallacies of relevance. There was the appeal to ignorance, a red herring. If there is no proof that the allegation is false, then it must be true.
The skit could have been funny if the report hadn't been suggesting Palin committed incest. That crossed the line.
But a person doesn't need this analysis to determine if something is funny. Either you laugh at it or you don't. I don't.