A Flying Monkey is someone who helps a bully-like individual harass or otherwise antagonize a target. They are usually persuaded to do this through manipulation, fear or other means.
To spot a Flying Monkey, look for those who are consistently supporting or speaking up for the bully-like individual, often putting down the target or attempting to discredit their boundaries and arguments. The Flying Monkeys might also be those people who are always around the bully-like individual, who act differently when they are in the presence of the victim and are cowardly when the bully is not around. Additionally, these people may engage in gossiping about the target or spreading misinformation, regardless of whether or not they have evidence to support their claims.