Is it permissible to mention the names of individuals to warn against their lying, and does this count as backbiting?

The questioner : May the Shaykh be respected, I know a person who walks with young men who lie and steal. Whenever I try to explain to the young men the danger of this person, they say: This is backbiting, so do not mention his name.

The Shaykh : This is a mistake. This falls under the category of advice. If you see a person doing something with another that is not permissible, convey it to him. This is not backbiting, nor is it talebearing.

The questioner : Should I mention his name?

The Shaykh : Mention his name. What is the benefit if you do not mention his name? Mention his name. Did you not know that the Prophet (peace and blessings be upon him) said to Fatimah bint Qays, when she came to him to inform him that three men had proposed to her: Mu'awiyah, Abu Jahm, and Usamah ibn Zayd—three men—so she came to consult the Messenger of Allah (peace and blessings be upon him and his family)? He said to her: , thereby pointing out the defects of these two men. One defect is one in which a person has no choice, which is that Mu'awiyah has no wealth. The second defect is one from which a person should rid himself, which is that he is a fornicator with women. So it is obligatory for him to make this clear to them. Yes, indeed. After that, there is an oath.