Question: What Kind of logical fallacy is This?

Dr. Bennett's answer is correct.
The general idea is that being successful in one field doesn't make you good at something else. If I am successful at business, that doesn't mean I'm also a great musician. I can be a great debater, but that doesn't make me an expert in every subject.
Also, this argument diverts from the issue. Anyone can be wrong about anything, even an expert.
If you are interested, Plato's wonderful dialogue Gorgias discusses this fallacy at length, especially in the first several pages. Socrates criticizes Gorgias b/c Gorgias is skilled at persuading people to believe things about topics that Gorgias knows nothing about.

http://classics.mit.edu/Plato/gorgias.html