First, EBarnacle, I think you need to check up on the meaning of Theory in the scientific world. It is different from the use of the word in everyday speech. From Wikipedia -
A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation.
I don't think Prof. Griffhorn's ideas quite satisfy that. Les is being generous when he says "It might be a hypothesis.". I don't think it gets beyond speculation.

Against my better judgement, I watched the programme.
Unless the epidemiological
The programme itself says that TB was found at other pre-Columbian sites in South America.
and genetic evidence
There have been Europeans in South America for nigh on 500 years and the indigenous population have a significant amount of European genes, mostly from Spain. Gosh.
If you can demonstrate a valid reason for the theory to be wrong,
Not how science works, EB. It is up to the proposer of a hypothesis to make predictions that are subject to falsifiability. There are none.
other than "He's crazy,"
Hmmm.

Another interesting take on it.