Ravindra Kumar, 32, was killed on Saturday after he remonstrated with the two men, who are alleged to have threatened him before returning with reinforcements and murdering him.
No arrests have yet been made, and police say they are trying to identify the suspects and are examining CCTV footage from a liquor store where the two suspected attackers were spotted.
One government minister praised Kumar on Twitter for promoting "Swachh Bharat", or "Clean India" -- a campaign Prime Minister Narendra Modi launched shortly after he took office.
The Indian premier has stressed the need to clean up India, urging citizens to pick up brooms and set about sweeping streets and other public places.
Man beaten to death in New Delhi for objecting to public urination
Modi, who is on an official four-nation tour of Europe, donated 100,000 rupees ($1,546) to the victim's family.
"The prime minister condemned the incident and directed the authorities to bring to book and punish the culprits for committing such (an) inhuman act," the prime minister's office said in a statement late Monday.
Kumar, who lived in a slum area of New Delhi, reportedly got married last year and was expecting a child with his wife who is seven months pregnant.
Modi has made sanitation and hygiene a major theme of his government, calling for every household to have a toilet within four years.
Last year he announced that his government had already built more than 20 million toilets since 2014.
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