Philosophers talk about secondary forgiveness in which Person B forgives someone who hurt his family member, Person A. Person B is legitimately hurt, although not directly, by the injustice perpetrated on Person A. Thus, he has a right to forgive if he chooses because he has been indirectly hurt by the injustice.
In the other example, of an ethnic or racial minority who has not been directly hurt, the norms of a given society still can be hurtful to his group. Thus, this person can forgive the abstract entity of society. The process can be more difficult because it is so abstract. One cannot see the norms themselves, only the outcome of those norms (such as behavioral or verbal disrespect). The forgiver may not even have specific people in mind and thus the process begins and ends with this abstract entity of “society.” Other than the one or ones singled out for forgiving, the process would proceed similarly to that in which Person B is hurt by Person C and then forgives Person C.