The 20-year-old student of history at St. Xavier's College here also said in an interview that he considered his grandfather and the Shiv Sena founder his favourite idol of modern India.
"We have no issues with the book being available in the market but it is being forced upon us. That is not acceptable," the younger Thackeray told IANS, referring to Mistry's novel that was taken off the syllabus of the university following protests by the Shiv Sena student wing.
"Criticism of policy is fine and acceptable. But here we have a book that is a part of our syllabus, which makes it impossible for us to avoid," he said, justifying his attack on the book.
The book, he said, used "foul language against many things that we, in Mumbai, hold close to our hearts. Most importantly, I think, opinions and facts should be treated differently."
Pointed out that Mistry's book had not led to any riot or unrest since it was published in 1990-91, Thackeray retorted: "Look, a criminal does not cease to be a criminal just because the crime was committed several years ago or the crime was not discovered for several years.
"In any case, we are mixing up the issues. We are unnecessarily getting into the past of the book. It has only been three years since it has been a part of our syllabus.
"And being a part of the syllabus is the only issue we are against. And in that sense I think the chapter is closed."
Aditya Thackeray was formally launched in politics Sunday at a function attended by his father Uddhav Thackeray and his grandfather.
But he clarified that he was "not exactly joining politics as it is being made out to be.
"While the Yuva Sena is certainly Shiv Sena's baby, the main motivation behind it is to make our youth aware of politics and civic issues.
"We will concentrate more on developing political and civic sense in youngsters and social activism."
Thackeray said he had no ideological disagreements with his father or grandfather. "The core issues remain the same to me. Maybe priorities have changed for my generation from my father's and grandpa's generation.
"They struggled for the country and injustices against Maharashtrians. My priorities, as of now, are more about youth and their issues."
Does he agree with the Shiv Sena's postures against "outsiders" entering Mumbai?
"As far as Mumbai is concerned, the issue was never really language," he said. "It is about civic limitations. Mumbai has its issues as a city. That is the problem."
Asked how he related to his uncle Raj Thackeray, who broke away from the Shiv Sena to form the Maharashtra Navnirman Sena (MNS), Adiya Thackeray replied: "No comments."
Q. What is your response to your college principal who said your movement against Mistry's book was wrong?
A. Again, he is my principal. I respect him for that. So, no comments about his comments.