The real danger in teaching “stranger danger” to children is to the children themselves. According to NCMEC, most (95%) of missing children are runaways, 5% are family abductions and only 1% non-family, i.e. stranger, abductions.
Children should be taught that if they feel threatened by a stranger, they should run to ANY other adult. Yes, a policeman is best, but is generally unavailable. Given the incredibly low odds that a child will be abducted anyway, the odds that two kidnappers would be in the same location are infinitesimally small.
I believe everyone reading this article would not hesitate to aid the child, although an SO would invariably experience some suspicion and perhaps harassment. Despite that, I would help without reservation.