Disrespect of the Prophet’s Family leads to misguidance and destruction of faith
There is a Hadith in Imam Baihaqi's Shu‘ab Ul Iman:
Translation: There are 6 people, whom I curse and the prayer of every Prophet is accepted. (Among them are the following)
The one who considers things declared forbidden by Allah as lawful.
Who considers those things lawful about my Family, which Allah has declared as forbidden i.e. who disrespects the Prophet’s Family. (Shu‘ab Ul Iman, Hadith No: 3850; Mishkaat Ul Masabeeh, Vol. 1, Pg No. 22)
This shows that disrespect of the Prophet’s Family leads to misguidance and destruction of faith.
There is a Hadith in Jame Tirmidhi.
Translation: The narrator of the Hadith says: When I went to meet Hadhrat Umme Salama (May Allah be well pleased with her), she was crying. I asked her: What is the reason for your crying? Hadhrat Umme Salama (May Allah be well pleased with her) said: I saw a dream in which the Holy Prophet's (Sallallahu alaihi wa sallam) blessed face and hair were covered with dust. Upon asking, He (Sallallahu alaihi wa sallam) said: I was present at Hussain's martyrdom in Karbala….." (Jame' Tirmidhi, Vol. 2, Pg No. 217, Hadith No: 3704)
The presence of the Holy Prophet's (Sallallahu alaihi wa sallam) in the Battle of Karbala is a striking proof of Imam Hussain's truthfulness.