There is precedence; the Rosenburgs, who did far less than most of this current batch.
They gambled they would not get caught, and they did. They lost. They die.
They knew in the beginning what the stakes were.
If I can forgive them or not, will effect my future karma, not theirs. They have made theirs and it may take them lifetimes to settle that karmic debt; this is their learning experience not mine.
If I forgive them, it will be better for me, but has no bearing on them or the decisions they made to arrive at the place they are at right now.