Yes, public displays of affection should be legalized in India as it is a form of speech, and India should legalize all forms of speech. That there is a ban on any sort of speech is awful and says much about India's government. India should reverse this line of thinking.
I think that it is harmless to display affection in public and I am personally at a loss as to why it isn't legal. Showing affection is simply a display of love. Love is wonderful and children should see that it's good. It definitely shouldn't be illegal. There is really no good or rational argument for banning it or making it illegal.