Actually, when people don't genuinely acknowledge the aggressive component of their assertive expression, healthy anger is masked and distorted. The result is often judgmental criticism, condescending sarcasm or, even, passive-aggressive retaliation. In other words, an assertive intention regresses into a hostile defense or intimidation. I encourage participants to think of the conflict as a power struggle issue.
People get seriously focused or start to squirm.
The antagonists are to verbal volley for about ten seconds. They can be loud and abrasive, hostile, whiny or passive-aggressive. Body language is encouraged. And then, after a few back and forths, they can reach closure, by saying whatever they'd really like to say to their imagined foe. However, the x-rated warning may not be sufficient.