Suppose that an extremely filthy man points out that there is a spot of dirt on your clothes. What will you feel?
Will you say that the filthy man, being so filthy, has no locus standii to point out the fact that your clothes are dirty? Will you feel insulted?
I don’t know about you, but I’d feel shame, not insult. The fact that the other guy was filthy would make it worse, not better. I would feel humiliated that I had to hear those words from such a man.
The fact that the filthy guy is not evenhanded in pointing out stains in others’ clothing would make no difference to me, because shame is between me and my conscience. Shame is what you feel when you have violated a principle that you hold dear. If you don’t feel shame, then it is easy to make it a point of honour and cry that you were insulted.