Hilchos Lashon Hara, Opening – negative commands (13)

Often people break another negative commandment as well: they embarrass a person about things from his past - for example, a low family background, not being smart, or not being successful - each person according to what hurts him.

Even if it happened with only the two of them there, he breaks the negative commandment (Vayikra 25:17), "A man shall not afflict his fellow." And all the more so if it happened in front of other people.