Ibn-e-Mujawar is liar. It is impossible for a Muslim to be disrespectful of Ali (RA) or to have "Bughz" with him. Bughz, Keena, Tabarra and Taqayyah are the specific and basic qualities of Shias.
If the statement you quoted is from Ibne-e-Mujawar's writings then due to his blatant lie , his all other writings become doubtful.
The fact is the both Shia and all of the Muslims have great respect for Ali (RA). The difference is that Shias exaggerate the status of Ali (RA) and this effort they do not hesitate to include fabricated stories to praise Ali (RA).
For example when they illustrate a fantasy story of his birth time how the walls of the Kaaba made a way for his mother etc. There is no comparison in Our beloved Prophet Muhammad pbuh and Ali (RA) but we do not hear any moon was split into half at the time Prophet Muhammad pbuh birth etc.