Maybe we can say that scammers are negatively intelligent or they are just lazy intelligent guys who could not harness their potentials but resorted to scamming.
Intelligent is a gift. If someone misuse the gift then he is an unfortunate man. It does not bring anything good for anyone.
Without being told, people are generally cautious around friends and family members who have a criminal record.
If I don't know the moves of my friend(s) then he is not my friend at all, it's just someone who you know a little. A friend even with criminal record still is a friend for you.