How to roleplay historical antipathy between character races

Traditionally, many character races in D&D have been defined to have a race with whom they share a mutual hatred: elves and orcs, dwarves and goblins, and gnomes and kobolds, for example. With Volo’s Guide, however, orcs, goblins, and kobolds are all playable races. How do we reconcile this in-story racial hatred with the meta requirement for characters in a party to support one another?