Memories of the decade-long armed Sikh insurgency - which peaked in the 1980s and in which thousands of people died - remain strong in India.
So when Canadian Prime Minister Justin Trudeau accused Delhi of involvement in the death of a Canadian Sikh leader, many Indians reacted angrily.
Mr Trudeau said Canadian intelligence was looking at "credible allegations potentially linking" the Indian state to the murder of Hardeep Singh Nijjar, a prominent campaigner for a separate Sikh homeland who was shot dead on 18 June in British Columbia (BC).
India has rejected the claim as "absurd".
As Delhi and Ottawa face-off in their worst-ever diplomatic row, Indian analysts, political commentators and leaders have been sounding off on social media.
Canada, Justin Trudeau and Hardeep Singh Nijjar have been the top trends on X (formerly Twitter).
One user wrote that Delhi had given a "befitting reply" to Canada while another said the government had "put Trudeau in his place".
India's main opposition Congress party - which has recently rarely been on the same page with the government - has also extended support and said there should be "no compromise of any kind in our country's fight against terrorism".
"Especially when terrorism threatens the sovereignty, unity and integrity of India. The interests and concerns of our country must always be kept paramount," party spokesperson Jairam Ramesh posted on X.
A prominent Sikh separatist leader, Mr Nijjar was shot dead in his vehicle by two masked gunmen on a June afternoon in the busy car park of the Guru Nanak Sikh Gurdwara in Surrey, a city about 30km (18 miles) east of Vancouver.
Delhi has previously described him as a terrorist who led a militant separatist group - but has denied any involvement with his murder.
A lot of reaction in India also reflected Delhi's official stand, with analysts saying Mr Trudeau's allegations could further sour relations with Canada.
"Canada and India are friends, not foes. But Trudeau, with his political alliance with Sikh radicals in Canada, has brought bilateral ties with India under increasing strain," wrote prominent commentator Bhrama Chellaney.
Others accused Mr Trudeau of "stooping" for Sikh votes - Canada is home to the largest Sikh diaspora outside state of Punjab.
Smita Prakash of the Asian News International (ANI) news agency said that by blaming India for Mr Nijjar's death, Mr Trudeau had already "tainted the investigation and judicial process by presenting his bias from a position of power and authority".
"He is asking for cooperation from India but blaming Indian authorities for the murder before that," she wrote on X.
Canada-India relations have grown increasingly strained in recent months. Mr Trudeau's meeting with Indian PM Narendra Modi at the G20 summit in Delhi last week was described as "frosty" and trade talks between the two countries have since been called off.
Mr Trudeau was also mocked after a problem with his aircraft forced him to stay back in Delhi for two extra days. Local TV channels and news websites ran reports about the "snubbed" Canadian PM's "disastrous" trip.
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