Over the years, the thousand-acre campus of Jawaharlal Nehru University has seen too many protests by its leftist student body to count, most of them petering out without incident. But one staged this month seems to have struck a raw nerve.

In all likelihood, the protest would have passed like the others, except that on this occasion, a television station broadcast footage from the event that it said showed the protesters shouting, “Long live Pakistan.” Equally offensive to many Indians, the students had gathered to express support for Muhammad Afzal, a Kashmiri militant executed for a 2001 suicide attack on India‘s Parliament in which nine people were killed.

Apparently, the twin insults were more than India’s newly empowered authorities from the conservative Bharatiya Janata Party, or B.J.P., could stand. Three days later, the president of the university’s student union was arrested on charges that included sedition.

Since the arrest, the B.J.P., with its strong Hindu nationalist roots, has gone on the offensive, casting itself as the defender of Indian patriotism. It has organized a countrywide campaign against the protesters, holding marches and rallies to defend “Mother India.” At one, in West Delhi, B.J.P. workers shouted, “The traitors of the nation, we will shoot them.”

By Wednesday, two more students had been arrested on sedition charges, and a debate over free speech raged in Parliament, with a Congress party lawmaker accusing the government of “trying to stifle the voice of the youth.”

The arrests have taken the tensions to a new level, with the B.J.P. calling the students “anti-national” and following up with a countrywide campaign against people viewed as unpatriotic.

Underlying the political issue is a historic ambivalence about freedom of speech in the world’s largest democracy. While free speech is enshrined in the Constitution, it has been undermined by various sections of the penal code, the courts and successive governments, and is not always supported by the public.

The Constitution provides for freedom of speech and expression, but with several exceptions, including speech that undermines “the sovereignty and integrity of India” or public order. The provisions are not unusual, but what has stymied freedom of speech, as a value and a legal right, is its history of being undermined for political gain by leaders across the ideological spectrum.

Dating to the colonial era, sedition charges have been applied broadly in successive governments, often targeting political opponents rather than people inciting violence, which is the aim of the law.

In 2012, a cartoonist criticizing corruption was charged with sedition, as were, briefly, a group of Kashmiri students cheering the Pakistani cricket team in 2014.

A law against acts “intended to outrage religious feelings” has been used to ban books and films, or to effectively erase them by compelling distributors to withdraw them because of litigation. The Congress government banned Salman Rushdie’s “The Satanic Verses,” fearing it would offend Muslims. Publishers withdrew another book, “The Hindus: An Alternative History,” by an American historian, Wendy Doniger, after a right-wing activist filed a case under the law, saying the book had a “hidden agenda to denigrate Hindus.”

Sedition was further reinforced in 1947 during the traumatic partition with Pakistan, which left hundreds of thousands dead as Hindus and Muslims turned on one another. Its continued use reflects a prevailing anxiety over such violence, even as some forms of vigilantism are effectively allowed free rein.

What precisely happened at J.N.U. is unclear, but several people have stepped forward to question the television report. A producer who worked on the segment said that editors had supplied inflammatory and false captions to explain the students’ unintelligible cries. The station denied the producer’s claim, and the editor of the station said in a comment to Press Trust of India, “Our systems are completely transparent and stringent not to permit any specific viewpoint to dominate any news broadcast beyond editorial merit.”

A student who attended the protest said there were calls for freedom from caste oppression, but did not recall anything about Pakistan.

However, there is no denying that the purpose of the gathering was to protest the execution of a militant responsible for multiple deaths in India.

A noted historian, Ramachandra Guha, maintained that the government had clearly overreacted in making the arrests, though the students’ hailing the man convicted of the Parliament attack was “a provocation where perhaps the freedom-of-speech limit has been crossed.”

Others have condemned the B.J.P.’s attempt to capitalize on the protest to further its nationalist agenda. “This whole idea that India’s always right on everything and anyone who raises questions is a traitor,” said Shekhar Gupta, a political commentator, “that’s a new thing.”

But the B.J.P. has enjoyed considerable public support. In an open letter, 33 people, including intellectuals and artists, said that the left was attempting to “cover up” the events at the university “in the garb of freedom of expression,” adding that “such slogans are unacceptable to all patriots.”

Critics of the government noted that a group of lawyers went largely unpunished after mobbing a courthouse where the student leader, Kanhaiya Kumar, was expected for a hearing, beating up students and reporters and shouting slogans, including “Hail Mother India.”

Two lawyers were arrested several days after the courthouse violence and accused of rioting and causing harm, but both were released on bail soon after. A third lawyer, issued a summons in connection with the riot, took five days to appear at a police station for questioning.

In contrast, Mr. Kumar, whose lawyer says he did not even participate in the protest, is still behind bars nearly two weeks after his arrest.

Prof. Harsh V. Pant, who teaches international relations at King’s College London, said it was hard for leftist opponents of the B.J.P. to aggressively defend freedom of speech because past governments, including those led by the Congress party, had undermined it before to further their own agendas.

“Where was freedom of speech in the past?” Professor Pant asked. “I do think the left is not on as strong a wicket as it might seem.”