Long term inbreeding and incest especially parent-children incest, will lead to the extinction of the population...
PLOS ONE: The Role of Inbreeding in the Extinction of a European Royal Dynasty
Incest leaves bumblebees facing threat of extinction - UK - The Scotsman
Indian tigers face extinction due to inbreeding and 'lack of genetic diversity' - Asia - World - The Independent
http://parkinson.cos.ucf.edu/Courses/PCB5556C/pdf/Frankham_98.pdf
Incest leaves bumblebees facing threat of extinction - UK - The Scotsman
Now you understand why and how Madhusree was right.
BTW, who cares? If Indians will get extinct, let them be. May be that is what nature wants. I told you anything that does not affect my personal life is not of my concern. Yes, I am toooooo much selfish.
About deceases coming from consanguineous/affinal marriages or inbreeding... it may be a news to you, such diseases are already there.
This research may help to explain why some genetic conditions are more common in India than elsewhere. For example a 25 base pair mutation in the MYBPC3 (cardiac myosin binding protein C) gene raises the risk of heart failure by seven times, and is found in about 4% of the Indian population. It is rare elsewhere in the world.
There is plenty of anecdotal evidence that recessive diseases are quite common in India, but they haven't been studied in any systematic way. The next steps are to look for the causal genes amongst these groups, and to study and assess more Indian populations.
Human Inbreeding and the Caste System: The Search for Human Inbreeding Defects
Your problem is that you are not ready to learn from others because of your arrogance. You assume that you already know everything and nothing exists beyond your knowledge. But I am not like you.
You lecture an Indian about India! WTF! Have you ever visited India... the townships and villages of Haryana, Rajasthan, UP and Bihar? Do you know what is happening there in the families? Listen buddy, India is not just Mumbai, Delhi and Bangalore. India is not what Indian members of PDF portray. Even you should not trust me if I tell you anything without referring to any academic studies. It is better you visit India if you really want to know about India.
You spend no time jumping to the conclusion that Madhusree was wrong. Who the hell are you to say that? Do you know how caste system works? Do you know there the villages and districts in India were the only and only occupation among all families is hereditary prostitution. Have you ever visited Rajasthan's Bharatpur? Have you ever visited any Indian brothel for that matter?
Yes.... the key to understand Indian society lies in the brothels. If you are interested in anthropology, you have to go to the brothels, the traditional ones which have been there for centuries. You have to know where the girls come from and what happens to them afterwards. You have to understand what happens in a Rajput or a Thakur's bedroom in Bihar or Uttar Pradesh.
I suggest you to collect this material and go through it.