You are correct in saying yelling is a sign of weakness, if that yelling is abusive. But as Annette wrote, strong and loud intervention is sometimes most appropriate.
Sweet story. Perhaps now the saint will give instructions on how to deal with the anger? Yelling at someone in anger makes things worse, can lead to physical violence, but so does repressing/suppressing it and "forgiving" too quickly, which can lead to psychosomatic illness. What to do? Anger is inevitable in life and is not "bad". Neither is sadness. These two emotions can heal if worked with appropriately. For instance, expressing the anger-in private- by hitting a punching bag and yelling, in order to release and reduce the energy of anger, or having a good cry to express sadness. There is a 99 cent kindle book available at Amazon which I found most helpful: "Anger Work--How to Express Your Anger and Still Be Kind". I'm not a shill--genuinely grateful for this wonderful book--only wish it was available in print so it could be more easily shared.
On Nov 12, 2013 Byron V wrote on Why Do We Shout In Anger?, by Unknown:
Explaining it IS expressing it...in a most healing way!