Shaykh Rabee said, “Insulting (a innovator), no you should not insult (a innovator).
If he was declared an innovator and there is a need to clarify his condition then clarify. Say so and so is a mubtad’i (innovator), so and so has such and such with him.
As for insulting then no, no insulting, do not insult if the scholars insulted him (the innovator), you do not insult even if they judged him with a judgment that is rightful.
If you see people being influenced by him in a harmful way then clarify his condition, so that the people can be cautious of his evil and safe from his evil.
As for insulting then no, it does not benefit.”
The Prophet (peace and blessings of Allah be upon him) said: “Trading insults with a Muslim is evildoing and fighting him is kufr (disbelief).” Bukhari & Muslim
It was reported in Saheeh al-Bukhari that Anas ibn Malik (may Allah be pleased with him) said: The Prophet (peace and blessings of Allah be upon him) was not a person who insulted people or used obscene language, and he did not curse people. If he wanted to rebuke anyone, he would say, “What is wrong with him? – may his forehead be rubbed with dust.”
Posted by Abdul Kareem Ibn Ozzie