All you can do is to politely advise him, preferably without your mother knowing.

I recently got to know that my mother’s brother works in an insuarence company and I don’t think he knows its wrong. Is it mandatory for me to tell him that working there is wrong. My mother does a similar work but when i told her its wrong, she got angry. Now if I tell her brother, she would get even more upset and that would cause problems in the house.