Do not embarrass your fellow-man
“Do not bear sin because of him” Vayikra 19:17, all the more so in public.
This is a great sin and our Sages said “Whoever shames his fellow man in public has no share in the world to come “Talmud Bavli 59a
We must take care not to disgrace anyone great or small.
Nor call him by a nickname by which he is embarrassed.
This applies specifically to matters between man and man.
However, in Heavenly matters if a person sinned and was rebuked privately and did not repent, he can be shamed publically and the sin publicised until he returns to goodness.