One thing I have noticed from critics is that they try defaming the Prophet by mentioning Ibn Ishaq and Tabari as their sources. In most of the stories where the Prophet (p) is alleged to have done something, they cite Ibn Ishaq as their source.
But as stated, many of these reports are not reliable because Ibn Ishaq does not give us the source of where he got the story from. One story which is frequently mentioned is of an old Jewish man. It is alleged by critics that Mohammad supported him being killed for throwing dust at him and the companions.
What they do not tell their folk is that the Prophet had nothing to do with this killing. In actual fact, when the Jewish man threw dust at Prophet Mohammad (p) and his companions, the Prophet told them straightaway to not touch him. But unfortunately, before the Prophet (p) finished his words, one of the companions struck the man.
Abu Khaythama, brother of B. Haritha b. al-Haritha, undertook to d so, and he took him through the harra of B. Haritha and their property until he came out in the territory of Mirba b. Qayzi who was a blind man, disaffected person.
When he perceived the approach of the apostle and his men he got up and threw dust in their faces saying, ‘You may be the apostle of God, but I won’t let you through my garden!’
I was told that he took a handful of dust and said, ‘By God, Muhammad, if I could be sure that I should not hit someone else I would throw it in your face.’ The People rushed on him to kill him, and the apostle said,
‘Do not kill him, for this blind man is blind of heart, blind of sight.’ Sa’d b Zayd, brother of b Abdu’l-Ashhal, rushed at him before the apostle had forbidden this and hit him on the head with his bow… 
When one reads the above, it is clear that the Prophet never endorsed or encouraged the man to be killed. So why are critics deceptively hiding the above, not mentioning the fact that Mohammad (p) forbade violence against the man? Why do they portray this story as if the Prophet (p) supported it when in actual fact he forbade it?
 Ibn Ishaq’s Sirat Rasul Allah – The Life of Muhammad Translated by A. Guillaume page 372 – 373