He said most of the people are from the 42 most marginalised tribes and have travelled 100km to be in Mumbai.
Many of these tribes were classified as "criminal" under British colonial rule. Despite the removal of this status, many of these tribes say prejudice still exists.
Many have not been able to get the benefits of affirmative action - a government policy which reserves jobs and educational places for India's lower castes - which the constitution of India guarantees.
Many of the tribes say the mass conversion is also a mark of protest against the Hindu caste system which has induced their social ostracism.