He wouldn't be near my child and I would have no hesitation reporting him to the police. Obviously he doesn't understand any other way.
And not all men think like that and neither do all young men.
My ex was young when we met and he always used car seats even in his hotted up car he had seats professionally fitted much to his friends disapproval.
Both my exs have done up cars and at one stage where young and ALWAYS used car seats. I guess they just take their kids lives seriously.