It's not just a myth that inbreeding is bad, it's a fact.
http://www.independent.co.uk/news/wo...g-8998115.html
"The filthy and severely deformed offspring of a horrifying incest cult whose members bred together for generations
have been discovered in a remote farming community in Australia.
Apparently unknown to the 2,000 people with whom they shared their fertile valley township in New South Wales,
at least 40 members of the reclusive Colt family raised four generations of inbred children in one of the country?s worst ever cases of child abuse........."