Ravan Dahan, where effigy of Ravan is burnt, is celebrated in some parts of Bharat during Vijaya Dashami day.
Ravan, though rakshasa, still considered as Brahmana. Some Puranas white of Rama, Hanuman getting Brahmahatya sin and doing expiations for that.
Now, is it morally right to burn, though in effigy form, of a Brahmana?
[This is not about characters of Ravana or his rakshasa character justifies. It's about whether burning an image of a Brahmana is acceptable/allowed.]
Burning Ravana effigy is probably influenced by how Lord Rama killed Ravana as per Ramopakhyana ( which is from a different Kalpa) -
Then Rama shot that terrible weapon of unrivalled energy, destined to compass Ravana’s death, and resembling the curse of a Brahmana on the point of utterance. And as soon, O Bharata, as that arrow was shot by Rama from his bow drawn to a circle, the Rakshasa king with his chariot and charioteer and horses blazed up, surrounded on all sides by a terrific fire. And beholding Ravana slain by Rama of famous achievements, the celestials, with the Gandharvas and the Charanas, rejoiced exceedingly. And deprived of universal dominion by the energy of the Brahma weapon, the five elements forsook the illustrious Ravana. And were consumed by the Brahma weapon, the physical ingredients of Ravana’s body. His flesh and blood were all reduced to nothingness,—so that the ashes even could not be seen.'""
Draupadi Harana Parva, Mahabharata.
As per Ramopakhyana, Mahabharata, Lord Rama burned Ravana alive to the point that not even Ravana's ashes could be seen.
