I would not consider an 18 year old a child and I would only help him if he asked me?

Seems to me you want to call the police on someone just because they are attracted to the opposite sex? 17 18 year old girls get hit on all the time by older men. In most countries they are getting married at that age.
If we are going to get the authorities involved every time someone hits on 17 or 18 year olds we are going to need 10 times as many police.
Seems like you people are advocating more govt. involvement in our lives.

Since when are 17 an 18 year olds children?

Not too long ago they were storming the beaches of Normandy.