From what I've seen, a lot of ICE agents are being malicious because they've convinced themselves that the people they're hurting are deserving of it somehow. They really think that they're the "good guys". Others crave the ability to power trip and bully people.
I'm not sure that trying to make most of them feel shame for what they do will work.
I might be wrong though. People's morality can be heavily influenced by their perception of their social circle's judgment of their actions. Letting them get a peek outside of their echo chamber might actually have an effect.