Counter-terrorism police encouraged an autistic 13-year-old boy in his fixation on Islamic State in an undercover operation after his parents sought help from the authorities.
The boy, given the pseudonym Thomas Carrick, was later charged with terror offences after an undercover officer “fed his fixation” and “doomed” the rehabilitation efforts Thomas and his parents had engaged in, a Victorian children’s court magistrate found.
A bad apple releases gases which causes other apples to quickly ripen and then spoil.
So it’s not just “there’s one bad apple therefore the bunch is bad”, the bad apple makes the other apples turn bad too. The saying is about an individual spreading corruption through a group.