“Instead of dying of old age, or by surgery, which causes a lot of suffering, the death Mr. Dabholkar got today was a blessing from God,” the leader, a former hypnotherapist now known as His Holiness Dr. Jayant Athavale, wrote in an editorial in the organization’s publication, Sanatan Prabhat.

With his unfashionable glasses and mild smile, Dr. Dabholkar fell into his region’s tradition of progressive social movements. An atheist, he quit practicing medicine at 40 to devote his life to activism. The room where he worked was bare but for a framed quote from Mahatma Gandhi. His wife, Shaila, recalled that her family had offered her an array of young men they considered marriageable, and she had chosen him for his idealism.

“We thought only about society, and that was what we spoke about,” she said. “Even though we were married, there was nothing like romance, or anything like that. Both of us were patriots of idealism. We wanted a good society.”

He was active on many fronts, from women’s rights to environmentalism, but the guru-busting received the most attention. A German scholar who wrote a book about Dr. Dabholkar’s group, the Committee for the Eradication of Blind Faith, described a traveling road show in which activists lay on beds of nails, set coconuts on fire and told crowds, “Just remember, miracles can never happen.”

“The rationalists do not shy away from challenging and provoking the gods, deities and spirits, ridiculing the people capable of controlling black magic and deliberately doing the most inauspicious things,” the scholar, Johannes Quack, wrote in his study “Disenchanting India.” “Some villagers told me that the rationalists would live to regret such behavior.”

Recently, Dr. Dabholkar had focused much of his energy on the anti-black magic bill, and he was frustrated that politicians were slow to embrace it. Shruti Tambe, an assistant professor of sociology at the University of Pune, said it had run into various roadblocks — a rise in conservative thought among middle-class Hindus; the vested interests of castes that specialized in certain rituals. Then there was the difficulty of providing a legal definition of superstition. The list of banned activities grew shorter and shorter over the years, and now includes 16 items, among them “to perform magical rites in the name of supernatural power” and “to perform so-called black magic and spread fear in society.”