In Sunan Ibn Majah page 12 Dhikr 'Ali we read...
In Sunan Ibn Majah page 12 Dhikr 'Ali we read: "On his way to Hajj, Sad met Mu'awiya and his companions mentioned 'Ali upon which Mu'awiya showed disrespect towards Ali, Sad got angry and asked 'why do you say such things?'" In the Arabic text the words used by Mu'awiya are "fanala minho" and the editor Muhammad Faula Abdul Bakee states in the footnotes that these words mean that Mu'awiya cursed and disparaged 'Ali.
If the word fanala does not mean curse / disparage then what was the reason for Sa'd getting angry? Ibn Kathir records that: "Sa'd bin Abi Waqqas said to Mu'awiya you have sat me next to you on your throne and begun to curse Hadhrath 'Ali" Al Bidayah al Nihayah" page 341 Volume 7 the Chapter "The virtues of 'Ali" This reference is enought to shut the mouths of the Salafi who love and admire the writings of Ibn Kathir, who they deem the definitive word when it comes to ascertaining historical facts - the Ibn Kathir that you worship cited the fact that Mu'awiya not just cursed but used vile language about Imam 'Ali (as).
Check out the link and weep! Ibn Kathir also records: "Mu'awiyah ibn Sufiyan ordered Sa'd [ibn Abi Waqas], saying to him: 'What prevents you from insulting (tasabb) Abu Turab?" Al Bidayah wal Nihayah, Vol. 7, Page 352, Chapter "The virtues of 'Ali" If the Nawawi party are to say that it doesn't mean anything bad, we should point out that the word sabb according to the Hans Wehr's dictionary that is the standard English-Arabic dictionary says: "Sabb.
To insult, abuse, call names, revile, rail at; to curese; to blaspheme, curse, swear." The only other meaning that the word has is to cause something, as in the word 'sabab' which means cause. Obviously the hadeeth has no meaning with this second meaning, so anybody who has even a basic knowledge of Arabic would know that the tradition means to curse or swear at somebody The improtant thing to note is that Mu'awiyah gave a command to Sa'd.
"He commanded him saying: What prevents you from insulting Abu Turab?" So it is not possible to say that he was merely asking a general question, but in fact the question was merely a way of giving an order, such as if you said to somebody "Why don't you give me that book?" intending to tell that person to give you a book.
The Syrian scholar Abu Zahra in his Tarikh ul Islam Volume 1 page 38 records: When Mu'awiya was proceeding to Hajj he saw Sad, grabbed him by the hand and sat him next to his pulpit.