Ok - Collins proposed that initiating violence against another is very hard due to built in inhibitions in most of us. Same thing that Grossman reviews. Granted there is some controversy over SLA Marshall's analysis but Collins looks at new data to say the basic idea stands up with troops reluctant to fire.
One has to overcome this reluctance. One component of that is to achieve a sense of emotional dominance over the opponent If that occurs, it is easier to initiate violence.
In some large group attack situations, the group achieves the dominance and that disinhibits their reluctance to attack. The victim folds and flees or ends up in the fetal position to reduce appearance of threat and minimize damage.
He documents that even armed personnel fall victim to this and if dominated don't use their firearms and can get beat up by unarmed groups.
I've seen folks in FOF unable to fire with Sims against an aggressor and land up on the ground as they retreated. One such person was a 'martial' arts expert and just froze up. He could have shot the aggressor.
Of course, one can postulate this will not happen to you because we are mighty - it is an empirical question.