When a person is very angry, the part of their brain associated with being reasonable and articulating reasonable thoughts more or less shuts down. Closed for business. Sign on the door — go away, can’t do this right now.
Yet in the midst of an argument, we still think to ourselves (or even say out loud), “Just be reasonable, can’t you?” Or maybe they say it to us. In a mediation, we may still want to say to a client, “Why can’t you be reasonable?” Or, more judgmentally, as one frustrated mediator put it to me recently, “Why can’t they just put their big boy pants on?”