How do I answer this ?

Given your further explanation below:

NAS75657 said:

My Son is Autistic and while I know we can’t let him hurt himself, hurt others and he has to respect others property, there is a way of teaching it without punishing, especially if there is always a reason behind the behaviour.

I'd suggest referring your father to these NAS resources, which explain the extent to which such behaviours can be unintentional and outside of our control:

NAS - Distressed behaviour

NAS - Meltdowns

NAS - Self-injurious behaviour

As these are published by a respected national charity, he might find them more persuasive than the book that he read.

On the plus side, it seems encouraging that he was willing to read the book in the first place. That perhaps suggests a willingness to learn, even though it might take some time for his knowledge to build, and his opinions to change.

Thank you 

Thank you