Ok try this on the "OnUserDefined" event of the NPC's you're using. To test I put it on a Half-Orc NPC blueprint and called them "elf-haters", then created a village of elf haters. They ignored my human PC, but yelled abuse and attacked my elf PC . Just change the RACIAL_TYPE_ELF to whatever race you want, and make sure you comment back in the User Event 1002 in the default OnSpawn script. Further instructions are in the comments.