Confirmation bias is the name given to the very human tendency to see what we want to see and seize on facts that confirm our prejudices, giving no weight to those facts which challenge them. It's why my usual approach to those who disagree with me or with whom I disagree is not to confront but to question or ridicule

There's a fascinating short article about the racial origins of Indians on the BBC site. The Hindu nationalist party, the BJP, has a racial purity view of Indian culture. The evidence of the genetic survey of Indians challenges their deepest beliefs and is therefore disbelieved - confirmation bias at its rawest http://www.bbc.co.uk/news/world-asia-india-46616574