Actually it is and especially when we know the song is talking about Durga maan when it says Maan. Durga being a Hindu Goddess cannot be imposed under secular law.
Even the Indian National Anthem, which may not be Hindu, but is either religious or is a poem written by Rabindranath Tagore praising George the IV at the time of his coronation.
Which makes the national song that Indians sing to be a song for their former colonial master:
O! Dispenser of India's destiny, thou art the ruler of the minds of all people[9]
Thy name rouses the hearts of Punjab, Sindh, Gujarat, the Maratha country, Dravida, Utkala and Bengal;
It echoes in the hills of the Vindhyas and Himalayas,
it mingles in the rhapsodies of the pure waters of Yamuna and Ganga
They chant only thy name.
They seek only thy auspicious blessings.
They sing only the glory of thy victory.
The salvation of all people waits in thy hands,
O! Dispenser of India's destiny, thou art the ruler of the minds of all people
Victory to thee, Victory to thee, Victory to thee,
Victory, Victory, Victory, Victory to thee!
Not to mention they need to remove Sindh from the anthem
I'm glad that Shiv Sena looks at us as a land of religious freedom
.