Speaking after a protest meeting here to express solidarity with the film crew, the former Union minister said it was a democratic right to make films with social and political commentary and if it has gone through the censor, no one has the right to object to it.
Alleging that the BJP was intimidating the film's producers, Mr Tharoor said it was totally unacceptable.
He said GST was a good idea that was "badly implemented" and the people are up in arms against it.
Consumers and traders are complaining and "everyone has the right to say that," Mr Tharoor said.
The actor's fans, who are in good numbers in the state, were treating the protest as an "insult" to him, the former diplomat said.
It was totally unjustifiable for a political party to demand cuts in the film, he said.
Mr Tharoor also justified the controversial scene in the movie that criticised the Goods and Services Tax (GST).
"They made an announcement that Vijay is Joseph Vijay," Mr Tharoor said, and wanted to know "whether we go for a film after looking at the religion of an actor".
Mr Tharoor also demanded that the film should be exhibited without removing the GST scene.
"The protest is against the BJP's attempt to infringe on democratic rights and freedom of expression," Mr Tharoor said.
The protest was organised by 'Vichar Vibhag' of the Kerala Congress Pradesh Committee.
The BJP had protested against the film over dialogues allegedly flaying the GST.
Tamil Nadu BJP leaders, including state unit chief Tamilisai Soundararajan and national secretary H Raja, have strongly opposed references to the GST in the just-released Tamil movie and claimed dialogues in it were "highly inappropriate".