Parsis didn't want converts because they feared "lower elements of Indian society" would sponge off the community charity

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All it takes is one drop of poison

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From: Luhrmann, T.M. "The Good Parsi: The fate of a colonial elite in a postcolonial society". Harvard University Press, 1996

Pages 164

Davar remarked that the community worried that the lower elements of Indian society - Bhangis, Mahars, Kahars, Dubras - would convert in order to gain access to the charitable funds reserved for Parsi Zoroastrians.