Shaykh Ibn Uthaymeen was asked:
Question: I am a History teacher and I have a problem oh Virtuous Shaikh. I pass during the explanation [of the lesson] some personalities who have been mentioned with evil traits, like deception, betrayal, breaking the covenant, arrogance, or deformity and other than that. These personalities are Muslim. Is my mention of these personalities with what is disliked considered backbiting?
Answer: “I see that a Muslim is not mentioned with evil, whether alive or dead because the Prophet (ﷺ) said:
لا تسبوا الأموات فإنهم أفضوا إلى ما قدمو
Do not abuse the dead, for they have reached the result of what they have done
[Al-Bukhari no. 6516]
As for the good qualities, then mention them because it helps in making supplication for this man and mention him with good. So that which I see is that if you pass by something from this and it is absolutely established that it occurred from this man which you are speaking about, then seek an excuse for him. As for it is not established, then Allah says:
وَلا تَقْفُ مَا لَيْسَ لَكَ بِهِ عِلْمٌ إِنَّ السَّمْعَ وَالْبَصَرَ وَالْفُؤَادَ كُلُّ أُولَئِكَ كَانَ عَنْهُ مَسْؤُولا
And follow not (O man i.e., say not, or do not or witness not, etc.) that of which you have no knowledge (e.g. one’s saying: “I have seen,” while in fact he has not seen, or “I have heard,” while he has not heard). Verily! The hearing, and the sight, and the heart, of each of those you will be questioned (by Allah).
[Reference removed since not available anymore]
Faisal Ibn Abdul Qaadir Ibn Hassan