Evidence?

While WSC's life is widely acclaimed as an outstanding example of bravery, insight, courage, and inspirational eloquence, amongst other attributes, he had to acquire all of them. Although his birth did mean that he met some very powerful and interesting people at an early age, he wasn't born with these attributes, but had to acquire them through experience, just as thou and I have a choice as to whether to do so or not.

Arthur Herman's book "Gandhi and Churchill", which was only recently published, is a "nitless" comparison of two recent historical titans. Neither man escapes criticism. Both shine with courage, and remarkable devotion to causes beyond their own survival or comfort.

Returning to the subject of the English-speaking world's opinions of Islam. When WSC wrote "The River War", few English-speaking people had any closer association with Islamic people than hearing the word "Mohammed" very frequently in Arab places of commerce. I imagine that that is why they called the religion of such people "Mohammedanism". In those days, the late 1890s, the British didn't have much of a reputation for admiring any other culture, and especially was this the case for military officers, whose encounters with Muslims were mainly with those on the fringes of Islamic society. Consequently, all that they saw was accurately and succinctly described by WSC in "The River War" passage that CF has quoted.

Not until Lawrence of Arabia (Col. T. E. Lawrence) earned the trust of desert Bedouins and their chieftains was much known in the English-speaking world about Islam. You can read a much more profound account of Islam, therefore, in Lawrence's "Seven Pillars of Wisdom".

In general, the heart of Islamic culture seems to me to be a more rural and traditional culture than the heart of Judaic or Christian culture, which seems to me to be more urban and progressive.

That would explain why Rory Stewart, who wrote the most recent widely acclaimed "Westerner's account" of rural Islamic culture ("The Places In Between"), is full of admiration for the decency, particularly honesty and generosity, of ordinary Islamic people. It would also explain why people who enter relationships with Muslims with a jaundiced and inauthentic view taken from someone with an axe to grind tend to find what they have been led to expect.