You're right. It's weird that people are rushing in here to defend inbreeding. What people might not realize is even when there's not a specific disease caused

You're right. It's weird that people are rushing in here to defend inbreeding. What people might not realize is even when there's not a specific disease caused by the inbreeding, there is still an overall negative effect on health, "inbreeding depression". Here is a paper that estimates the effect in humans: https://www.ncbi.nlm.nih.gov/pubmed/26131930 https://www.ncbi.nlm.nih.gov/pubmed/26131930.