"We are definitely going to oppose it," Muthalik said after his release on February 2.
"We would also request colleges also to stop the celebrations. After all this we will start our crusade."
Valentine's Day has become increasingly popular in India in recent years, led by retailers selling red balloons, velvet pillows and teddy bears, but some see the festival as symbol of a the growth of Western culture.
Police detained activists from Shiva Sena, a right-wing political party, who had taken to the streets in the city of Gwalior in central India to criticise Valentine's Day as anti-Indian.
Indian women fight against repression
"Activists of Shiv Sena were staging a peaceful demonstration against western culture and were doing good for Indian culture," Narendra Singh Tomar, the district head of Shiva Sena, said.
"But administration is creating hurdles in our way. Administration is trying to stop us although we are protecting Indian culture.
"We want to say protecting Indian culture is neither a sin nor a crime."
Police said that they feared the protesters would engage in "hooliganism".
Another five members of Shiv Sena were arrested in New Delhi afetr threatening couples in a park, a police spokesman said.
Nishan Susan, a journalist who launched a campaign on Facebook, the social networking site, after the Mangalore attack told Al Jazeera that the pressure from conservative Hindus had angered many Indians.
"It's not that one is dying to go to a pub everyday or celebrate Valentine's Day, these are not important things," he said.
"There's this horrible sense that you have to look over your shoulder all the time."