Why do fancy pants, latte-sipping, Prius-driving liberals say that inbreeding is bad?

What a bunch of snobs. Let's take a look at a society, Iceland. Iceland has 300.000 people with very few foreigners, thus, we all know that the population has to be inbred to some extent, but yet Icelanders are beautiful, healthy, intelligent, prosperous (even with the financial crisis) and free, yet the elitists libs want to make it illegal for us to marry our sisters because they claim it is bad for potential children. Well I would like to point out to these Euro worshippers that a country that is part of their favorite continent is the product of inbreeding and it worked out rather well.