Protesters gathered outside Madison Square Garden in New York on Saturday as Mohan Bhagwat, chief of the Rashtriya Swayamsevak Sangh (RSS), spoke to thousands inside the venue.
Demonstrators carried placards and cutouts of Bhagwat, with images from the protest showing accusations that the RSS is a fascist organization and responsible for the assassination of Mahatma Gandhi.
The event, titled "Universal Oneness Celebration" and organized by American Hindus for Engagement and Dialogue, drew about 5,000 members of Indian American groups to the Infosys Theater inside the arena.
Beyond the street protests, New York Mayor Zohran Mamdani said he opposed the event, and a US panel on religious freedom called for sanctions.
Speaking at the One World: One Humanity Faith Leaders' Summit, Bhagwat said a Hindu who believes there should be no Muslims in Bharat would "not remain Hindu".
The RSS, founded a century ago, is widely considered the ideological parent of India's ruling Bharatiya Janata Party (BJP). Prime Minister Narendra Modi, a polarizing figure both in India and among the diaspora, came up through its ranks.
Critics accuse the group of promoting Hindutva, an ideology that defines Indian culture and national identity in terms of Hindu values. The BJP and its affiliates have also been accused of fostering intolerance and of human rights violations, including mob lynchings, attacks on minority places of worship and the demolition of Muslim-owned properties.