Conflict resolution training only helps when the problem is that people’s communication skills are weak in ways that cause them to escalate conflicts unnecessarily. In that situation, learning better communication (and especially listening) skills can make a big difference. But, not every problem is like that.
When someone is intentionally cruel, it’s not a problem with their social skills. It’s a problem with their values.
Teaching a cruel person communication skills will not cause them to become kinder or teach them to respect others.
Similarly, teaching victims of intentionally cruel people conflict resolution skills will not solve the conflict. It just teaches both parties to blame the victim. Cruelty happens because of choices cruel people make, not because their victims lack conflict resolution skills.
Putting abusers and victims together in a conflict resolution training *especially* will not help. All that does is send the message that no one is really in the wrong, and that there is just a communication problem that needs to be worked out.
Sometimes, conflicts are not mutual. Sometimes, one side is in the wrong in all of the ways that are important. Sometimes, people are choosing to be mean. Treating a cruelty problem as a social skills problem makes everything worse.