"In two empirical studies, we examined the unexplored psychological consequences that follow from a harm-doer's explicit refusal to apologize."

In most cases there is no single harm-doer. In one-on-one relationships, one party can nag for a long time until the other party explodes verbally.

In group settings a group can harass, obstruct and libel an individual until that individual explodes.

You need the full background, which is missing in modern mob justice, because the individual is de-platformed and shamed without an opportunity for clarification.