As Dawkins once mentioned in a charpter from one of his books, something can sound immediately ridiculous; the more you think about it, the less ridiculous it gets (Can't remember what exactly he wrote).

But there are also things, which do not appear that ridiculous, but the further you think of them, the more ridiculous they will get.

To someone here, Tai Cu’s idea might not first appear to be ridiculous.

Nevertheless, if we follow his thought, things can get out of hand fairly easily.

Like this. Inbreeding couples stand higher chances babies with severe genetic disorders. In the future we should able to deal with a wider spectrum of these diseases. One day, we could beat all of them. But that does not mean we should all celebrate and go to have sex with someone on the same branch of the family tree.