Justification

I was wondering what the theological justification was for calling for the death of non-Muslims who are deemed to have insulted the Prophet. This Islamist screed provides it:

At the time of the Messenger Muhammad (saw) there were individuals like these who dishonoured and insulted him upon whom the Islamic judgement was executed. Such people were not tolerated in the past and throughout the history of Islam were dealt with according to the Shariah. Ka’ab ibn Ashraf was assassinated by Muhammad ibn Maslamah for harming the Messenger Muhammad (saw) by his words, Abu Raafi’ was killed by Abu Ateeq as the Messenger ordered in the most evil of ways for swearing at the prophet, Khalid bin Sufyaan was killed by Abdullah bin Anees who cut off his head and brought it to the prophet for harming the Messenger Muhammad (saw) by his insults, Al-Asmaa bintu Marwaan was killed by Umayr bin Adi’ al-Khatmi, a blind man, for writing poetry against the prophet and insulting him in it, Al-Aswad al-Ansi was killed by Fairuz al-Daylami and his family for insulting the Messenger Muhammad (saw) and claiming to be a prophet himself. This is the judgement of Islam upon those who violate, dishonour and insult the Messenger Muhammad (saw).

Shortly after these incidents the people began to realise that insulting the Messenger of Allah (saw) was not something to be taken lightly and that by doing so would mean that you would be killed for it, a concept that many have seem to forgotten today.

The insulting of the Messenger Muhammad (saw) is something that the Muslims cannot and will not tolerate and the punishment in Islam for the one who does so is death. This is the sunnah of the prophet and the verdict of Islam upon such people, one that any Muslim is able execute. The response of the Muslims all over the world shows us the inability to deal with such people, the kuffar are attacking our Messenger and are allowed to get away with it whilst the Muslims have no power to do anything about it.

So, if this is right, it's not just a case of some angry people who need to get a grip (as many of the liberal sites seem to regard it). It's in there. It's bound and bred in the core of the religion.