Considering how the 1st Reconstruction got cancelled, and the Nazi elements that persist in Germany, I think that there is a great deal of evidence that mercy doesn't work against systemic evils. The whole concept of Nazi, Confederate, and now MAGAT, ideology should go on trial...with death being the sentence if a whole class of participants are found guilty.
Worked for ICE? You die.
It isn't kind, nor just. But this disease of evil needs to be uprooted, else it will spread into future generations of the nation. The Confederates and Nazis have proven this.