Historians have been free to delve into the origins of Christianity for a couple of centuries. Not so with Islam. To the faithful, its origins are off-limits to scholarship and truth-seeking inquiry. That would be alright if the sway of the faithful only extended to the lands of historic Islam. What happens in Islamic countries is by and large their own business. But now, thanks to migration, the sway of the faithful extends into the West.
The latest case: threats of violence have led Channel 4 to cancel a screening of Islam: The Untold Story, a documentary by Tom Holland, a bestselling historian. (It was part of a series on several religions, but predictably only the Islam episode provoked outrage.)
His investigation into its origins claimed that there is little written contemporary evidence about the prophet Mohammed. … He also suggests the Koran makes little or no reference to Islam’s holy city of Mecca, and argues there is no evidence for the general assertion that Islam began ‘fully formed’ in the 7th century. (more)
It looks like Holland is trying to convey the highly respectable theory known as Hagarism to a popular audience. In brief, the theory is that Islam did not make the Arab empire, instead the Arab empire made Islam. Not an especially strange claim if you apply the idea to other historic empires and religions. I do not know if the theory is sound, but I do know that it is intolerable for threats of violence and howls of outrage to silence historical scholarship and its dissemination.