DY:
Your fear about negative influences has a point of merit, but is also a source of grave danger. I do not want my child exposed to many of the decadent influences of today’s world. However, not every kid that slips into most of these traps brings them to peers to dendanger them. It is widely believed, for instance, that a kid that begins dabbling in drugs is a rodef. This is sometimes true. But many times, it is not. The child needs treatment for a disease, not punishment for a crime. Many drug users want their addiction to remain hidden, and they withhold it from their peers like they hide it from others. Meanwhile, there is an absolute chiyuv to ascertain the “rodef” status before committing the spiritual murder of throwing this kid into the welcoming arms of the street.
Yes, kids who are exposed have a greater yetzer horah. Does this sentence anyone who knows the kid? You are correct that any exposure is major exposure. But this does not necessarily expose others. This needs to be determined on a case-by-case basis, not by policy.