I agree with you that we as Christians should humble ourselves and pray, seeking God's face, asking His forgiveness and mercy, both individually and as the body of Christ, and that we should forgive people who do evil things against us personally. It's just that I don't think that we have power to forgive sins that were committed against other people. Only the victims themselves, if they are able, whose blood cries out from beneath the rubble, and God Himself can do that.
Cordially,
Agreed. The call to personal repentance in no way obviates our obligations to the innocent victims of September 11, much less to prevent the victimhood of those whom the murderers would target next.