陪你开枪的人很多替你挡子弹却很少
[péi nĭ kāi qiāng de rén hĕn duō tì nĭ dăng zi dàn què hĕn shăo]
This nickname reflects the fact that many people may be willing to assist someone in attacking others (metaphorically), but few are truly willing to stand up and protect them when they're in trouble. It implies a certain level of superficiality in friendships or acquaintances.