It is nice to ask if it is a good time for someone to hear a complaint, grievance or to be confronted. If you just launch into it with an unsuspecting person, they will not be able to hear what you are saying.
Timing and permission are everything. I remember being at seminar years ago, and we were eating dessert after dinner. It was an amazing chocolate cake with gooey, shiny chocolate frosting. The kind of cake that if you like chocolate, you cannot resist.
I was listening to a couple of women who were so angry at a certain man for some inappropriate behavior. I did agree, however I saw that he was enjoying a piece of this incredible chocolate cake and so advised the two women to wait until he was finished eating his cake. It seemed only civilized and appropriate that they should wait. It was a sacred few minutes. They did not listen to me and confronted him anyway. I am sure his enjoyment of the cake was now ended, and he may even associate chocolate cake now with being attacked verbally by angry women.
I felt sorry for him, and wished they had waited. I am pretty certain he did not hear what they were trying to convey. I enjoyed mine for him.