Please read again…
He is suggesting that the stance of Hindu extremists that India should be purified (shudhhi) of non-muslims by their conversion to Hinduism is not practical since you cannot really convert into Hinduism with caste system.
And “this guy” “Ambedkar” is one of the most respected intellectuals for all in India (Muslims, Hindus and Budhs).
And further for your information:
In the Persian language of the Sassanian period, Hindu referred to the inhabitants of the area around and beyond the Indus River, or Hind - the people who were followers of Hinduism. The name is also said to be a corruption of Hindu Koh, from the (modern) Persian word Kuh, meaning mountain. James Rennell, writing in 1793, referred to the range as the “Hindoo-Kho or Hindoo-Kush”[4]](http://en.wikipedia.org/wiki/Hindukush#cite_note-3).