Divine punishment to the one who disrespected
Imam Hasan (May Allah be well pleased with him)
The famous Hadith-expert of 6th century Hijri Imam Abul Qasim Ali bin Hasan famously known as Ibn Asakar (May Allah shower His Mercy on him) relates a Tradition from the famous Successor Imam A’amash (May Allah shower His Mercy on him):
Translation: It is narrated on the authority of Hadhrat Imam A’amash (May Allah shower His Mercy on him), a wretch defecated on the blessed grave of Imam Hasan (May Allah be well pleased with him). He immediately went mad. He kept barking like a dog until he died. Even after his death, horrible sounds of barking could be heard (from his grave). (Tareekh Dimashq, Vol. 13, Pg. No. 305; Jame’ Karaamaat Ul Auliya, Vol. 1, Pg. No. 131)
Imam Yousuf Nabhani (May Allah shower His Mercy on him) has also related this in his book Jame’ Karaamaat Ul Auliya on the authority of Abu Nu’aim and Tabaqaat Munaavi.
This shows that if the beloved of Allah Most High are insulted, then such punishment is given that the world remembers it for a long time. Allah Most High took away all sense from that person and made him a lunatic. His lunacy was not the usual lunacy. Instead that person would bark like a dog. He lived his life like this and died in the same state. When he died, the sounds of barking could be heard from his grave.
This incident is a great lesson for the whole Ummah. May Allah Most High guide us all to be respectful and reverent.