Agree with you. His reply is a bit weird unless it was misquoted by media. To me a 17 year old is still a kid and immature in thinking. Despite there being mature teens of that age, their life experiences at that age may not be enough to make a wise decision unless in a desperate situation i.e. where they have no adults to depend on.
As someone more than 40 years her senior, he should know better.
If the lady involved is in her mid 20s onwards and chose to get involved with a man 40 years her senior, then she should be well aware and take responsibility on any consequences of her actions.