You might want to gently share one of your own stories of forgiveness when the group is in a quieter state. Showing forgiveness through your own story could be the beginning of teaching your friends about what forgiveness is and what it can accomplish. With this approach, you are not demanding forgiveness from them, but instead are giving them a chance to see it in action as you describe what you did and the effects of forgiveness on you. With this approach, you might be establishing a new norm, one of forgiveness, into the group.
For additional information, see: Choose Love, Not Hate.