A person tends to challenge people who are close to them. That's why we often see couples and families challenging each other and end up hurting each other.
老師 (讓小朋友出校車後): 別嬉戲，別跟陌生人說話。 (請填空)
Teacher (after letting kids out of the school bus on a field trip): No horsepay. Don't talk to strangers.