The Crips and Bloods
The ongoing feud between the notorious Crips and Bloods is similar to the conflict between the Montagues and Capulets in that there is no doctrinal or principal at issue between the groups. Both gangs have been indoctrinating their members with hatred of the other group as a fundamental defining value of their group, but without any specific reason to justify the hatred in the first place. Like many other conflicts, the mutual hatred and antagonism in continually fueled by instances of violence and deliberate insult that each believes it must avenge to save face and reputation.
As in the case of the Montagues and Capulets, it is specific incidents that provide the motivation for retaliation rather than any conflicts in beliefs or values.
If anything, the Crips and Blood actually subscribe to identical values and norms such as their focus on illegal activities like prostitution, drug sales, and external displays of apparent wealth and power in the community. Nevertheless, the socialization process of new gang members ensures that members of both groups continue to detest one another. That is not substantially different from the way that multi-generational family feuds continue long beyond the lives of the first generation to harbor those sentiments. It is also quite similar to many of the ongoing sources of resentment between different religions whose history often recount the atrocities committed by one another over many centuries while largely discounting their own.