Hitting a woman is never acceptable.
Gerald and his girlfriend Ellen are in an intense argument and Ellen has just levied a serious insult at Gerald's family.
Gerald wants Ellen to know that what she said is not okay.
Gerald leaves the house to cool down and comes back later to talk with Ellen about how she crossed a line.
Gerald slaps Ellen across the face after she makes the insult.
Gerald and Ellen both have a chance to get a handle on their feelings and regain perspective, so they can have a productive conversation.
Ellen is enraged and escalates the physical confrontation which ends with the neighbors calling the police on the two.