[Lurker]

In Christianity we are told to forgive

Christ never said anything about forgiving the unrepentant murderer. Ever.

Read Luke 17 3-4.

Christians are told to forgive the truly repentant who ask forgiveness. None of the monsters who trained and sent these monsters has repented, and none has asked for forgiveness.

Therefore forgiving them is a decidedly un-Christian thing to do.

L

[Tamar1973]

Not to mention the fact that although we have the right to forgive whoever sins against us>/b>, it is not our place to forgive those who sin against others.

[Chickensoup]

Forgive them for they know not what they do
Meaning

Jesus’ words from the cross, asking forgiveness for those who put him to death. More widely, of course, the plea was for all humanity.

Origin

From the Bible, Luke 23 (King James Version):

23:33 And when they were come to the place, which is called Calvary, there they crucified him, and the malefactors, one on the right hand, and the other on the left.
23:34 Then said Jesus, Father, forgive them; for they know not what they do. And they parted his raiment, and cast lots.