The ethical issues surrounding dogs are entirely different from those surrounding people. Additionally, humans didn't specifically select for traits in other people which caused genetic disorders to become rampant in an entire bloodline (with some accidental exceptions I suppose).
Specific selection? Not with that knowledge in mind admittedly but some groups of people continue to inbreed regardless of the clear dangers of this for offspring. There is a country where 70 percent of all marriages are between first cousins. The results are dire.
