Forgiveness of others is required of all who bear the name of Jesus. Those who refuse, cannot be associated with Christ, for in doing so they also refuse to extend compassion as their Master has extended it to them. In order to forgive others, it is necessary to will it as Christ himself willed to die on the cross for our sake.
The task of participating in Christ’s mission of salvation is not optional. It is one of the reasons you were created. If one should refuse, he may hear those terrifying words: “Throw this useless servant into the darkness outside, where there will be wailing and grinding of teeth.”