The usual lies spread about the Prophet (p) is astonishing. It is alleged by critics that Habbar Ibn al-Aswad bin Ka`b al-`Ansi was killed because he was a liar who claimed to be a Prophet. However, this is not the reason why he was killed. Aswad persecuted many Muslims. He was a warmonger.
In one report he struck the daughter of the Prophet (p) Zaynab – at the time she was pregnant. Because of Aswad’s action, she lost her baby. In other occasions, he waged war against the Muslims. Hence his fate came to an end when one of the companions killed him. So, he is not as innocent as critics make him out be.
It was reported that Habbar used to relate [the following story]: When the Prophet came out and preached [the belief in] Allah I was among those who showed hatred toward him, opposed him, and harmed him. [When] the Prophet sent someone to Mecca to fetch his daughter Zaynab some people from the Quraysh obstructed her way, and Habbar was among them.
He poked her and wounded her back with a lance, and she lost the baby she was carrying; she was then brought back to the dwellings of the Banu Abd Manaf. Habbar b. al-Aswad had committed a grave sin against Islam, and the Prophet allowed his blood to be shed with impunity.
Whenever he sent a party on a raid he gave orders concerning Habbar, saying ‘If you seize him put him between two logs of firewood and burn him.’ He would then say: ‘Only the Lord of Fire is entitled to torture with fire.’ If you seize him cut off his hands and feet, then kill him.’ 
Maulana Wahiduddin Khan:
Habbar ibn al-Aswad, who had been responsible for great persecution of the Muslims. When the Prophet’s daughter Zaynab, wife of Abu’l ‘As, was on her way from Makkah to Madinah, he stabbed her camel’s side with a spear. The camel went into a frenzy and Zaynab fell down.
She was with child at the time. Not only did she suffer a miscarriage, but the effects of the mishap remained with her for the rest of her life. Orders were given for him to be killed, but he came to the Prophet and pleaded for mercy. ‘Prophet of God,’ he said, ‘forgive my ignorance. Let me become a Muslim.’ The Prophet forgave him. 
Professor Taha Jabir Alalwani
When the Messenger of God entered Makkah victoriously in the year 8 AH/629 CE, he had instructed his leading men not to kill anyone but those who had fought against the Muslims, as he wanted Makkah to be conquered peacefully. However, he did order a group of individuals, whom he named specifically, to be put to death even if they were seeking refuge under the covering of the Ka’bah.
The group included six men and four women, namely: Ikrimah ibn Abi Jahl, Habbar ibn al-Aswad, Abd Allah ibn Sa’d ibn Abi Sarh, Miqyas ibn Subabah al-Laythi, al-Huwayrith ibn Nuqaydh, Abd Allah ibn Hilal ibn Khatal al-Adrami, Hind Bint Utbah, Sarah, the servant of Amr ibn Hisham, and Abd llah ibn Khatal’s two song-stressed, Fartana and Quraybah, who was also known as Arnab. The reason for this was that these individuals had incited the polytheists to go to war against the Muslims and prevent them from following in God’s path. 
 The History of al-Tabari – Biographies of the Prophet’s Companions and Their Successors: al-Tabari’s Supplement to His History, volume 39, page 70
 Muhammad: A Prophet for All Humanity By Maulana Wahiduddin Khan page 331
 Apostasy in Islam: A Historical and Scriptural Analysis By Taha Jabir Alalwani, page 50Advertisements