A well-known story: one day the Prophet's grandsons, Hasan and Husayn (a.s.), saw an old man who was not performing the ritual ablution (wudu) correctly. They did not want to embarrass him.
So they approached him kindly and said: “We are arguing about which of us makes wudu more beautifully. Please watch us and tell us who does it better.” One after the other, they performed wudu. The old man watched closely and said: “You both did everything right. I was the one doing it wrongly – and now I have learned it from you.”
What we learn: we can teach others kindly, without embarrassing them.