To start off with, here is a summary of how Muslims viewed Europe, by Carole Hillenbrand:

"Western Europe held few attractions to the medieval Muslims; from their perspective their own culture was so obviously more sophisticated and advanced. The medieval Muslim felt superiority and condescension towards Christians. For him it was indisputable that Christianity, an incomplete and imperfect revelation, had been superseded and perfected by Islam, the final Revelation, and that the Prophet Muhammad was the seal of the prophets. Such supreme confidence in the values that were based on this Revelation did not engender great intellectual curiosity in peoples of other faiths which were by definition wrong or incomplete. The Muslims showed little interest in Christianity, whether it was the Latin Christianity of the barbarians of western Europe, the eastern Christianity of their great enemy and neighbour, Byzantium, or the Oriental Christian communities who had lived under Muslim rule since the Arab conquests in the seventh century. The Muslims knew little and cared less about Europe; it just did not impinge much on their world view. They knew a certain amount about Christianity from the Christian communities in the Middle East, but even to those familiar groups they gave scant attention." (Hillenbrand, pg. 267-268)

So medieval Muslims didn’t think much of Europe and Europeans, if they ever thought about them at all, and they didn’t make a great effort to learn about them; this was basically the same situation the other way around, since Christians also didn’t really know anything about Islam and didn’t care to find out. Islamic philosophy and geography was ultimately based on the 2nd-century geography of Ptolemy, who divided the known world into seven regions. Muslim geographers did the same, and while of course the Middle East and North Africa were the best regions, and inhabited by the best people, other peoples lived in more inhospitable climates and their personalities and characters were negatively affected. Europeans were generally known as “Franks”, and they lived in a zone where

“they pursued the arts of war and the chase, were of melancholic temperament and prone to savagery. They were also filthy and treacherous.” (Hillenbrand, pg. 270)

Al-Mas’udi in the 10th century was one of the first encyclopedic geographers. About Europeans, he wrote:

"The power of the sun is weak among them because of their distance from it; cold and damp prevail in their regions, and snow and ice follow one another in endless succession. The warm humour is lacking among them; their bodies are large, their natures gross, their manners harsh, their understanding dull, and their tongues heavy. Their color is so excessively white that it passes from white to blue; their skin is thin and their flesh thick. Their eyes are also blue, matching the character of their coloring; their hair is lank and reddish because of the prevalence of damp mists. Their religious beliefs lack solidity, and this is because of the nature of cold and the lack of warmth." (Hillenbrand, pg. 270)

Muslims who lived in or visited Europe held the same views, even in multicultural areas where Muslims and Christians lived together, like Spain and Sicily. In 1154, al-Idrisi published the Book of Roger for the Christian king Roger II of Sicily. Al-Idrisi was familiar with Italy and the Mediterranean region, but otherwise the book was full of Ptolemaic and more recent Muslim geography, so that anywhere further north, like France and England, were described as full of ice and snow and surrounded by the freezing cold sea. (The Book of Roger is significant today because it also contained dozens of maps, unlike most geographies at the time.) Ibn Jubayr is another example - he was from Spain, and travelled all around the Mediterranean, including Sicily and the crusader states. He was sometimes impressed with the Christians in Sicily and Jerusalem, but otherwise he mostly tried to avoid them, since they were dirty, smelly, unhygienic, unclean, etc.

For authors from Syria or Egypt who were familiar with Frankish crusaders, all the same stereotypes appear, but now supplemented with real-life examples. The source that is cited most often here is probably Usama ibn Munqidh, a 12th-century poet, soldier and diplomat from Shaizar in Syria who lived in Damascus and Egypt and often visited the crusader Kingdom of Jerusalem. He thought the that

"Among the Franks there are some who have become acclimatized and frequent the company of Muslims. They are much better than those recently arrived from their lands, but they are the exception and should not be considered representative." (Book of Contemplation)

Among his various examples, he mentions a European knight who has never a Muslim praying before, and he tries to correct Usama before some native Frankish knights whisk him away. Clearly these new arrivals were big dumb idiots.

One of Usama’s most famous anecdotes is about a Frankish knight who discovers the concept of shaving his pubic hair, when he sees a clean-shaven Muslim man in the public baths. This is a second-hand story from a man Usama knew, who ran a public bathhouse:

“I once opened a bath-house in Ma'arra to earn my living. Once, one of their knights came in. Now, they don't take to people wearing a towel about their waist in the bath, so this knight stretched out his hand, pulled off my towel from my waist and threw it down. He looked at me – I had recently shaved my pubic hair – and said, 'Salim! Then he moved in closer to me. He then stretched his hand over my groin, saying, 'Salim! Good! By the truth of my religion, do that to me too!' He then lay down on his back: he had it thick as a beard down in that place! So I shaved him and he passed his hand over it and, finding it smooth to the touch, said, 'Salim, by the truth of your religion, do it to Madame!' - madame in their language means 'the lady', meaning his wife...So I shaved her hair there as her husband stood watching me." (Book of Contemplation, pg. 149)

This is obviously a very silly story, and whether or not it is literally true isn’t really the point - Usama is stelling stories about stereotypical dumb-dumb Franks because he knows his audience will also know all the stereotypes and jokes. It’s the equivalent of telling dumb blonde jokes, or similar regional jokes wherever you’re from (Polish jokes in Europe? In Canada we have Newfie jokes). This is because in addition to all the more academic geographical works, Franks often appeared in popular Arabic literature and folk tales as lumbering brutes. They were skilled in warfare but not much else. So when Usama tells stories like this he’s using his real world observations to make jokes that everyone would have understood as a regular part of Arabic storytelling.

The knight who wants his pubes shaved is pretty hilarious but it also illustrates just how different Usama and other Muslims saw their morals and Frankish morals. First, the guy just walks around naked in the bath; he has no proper sense of decency like Muslims, who covered up with a towel. He doesn’t shave his body hair, so he’s unclean and unhygienic. He says things like “by the truth of my religion”, something a Muslim would say but a Christian probably wouldn’t - and Usama is making fun of him again because everyone knew Christianity obviously wasn’t the true religion (the knight also says “by the truth of your religion” - he’s so dumb he doesn’t know both religions can’t be true). And then the big punchline, he brings his wife in, everyone stands around naked, and her pubic hair gets shaved too! That would never happen in a Muslim bath because Muslim men and women didn’t interact in public the way crusader men and women did. Frankish women had more freedom to walk around by themselves and talk to strange men - from a European perspective we might think that’s a good thing, but medieval Muslims did not think so. But were the knight and his wife real people? Probably not, it’s just a joke with stock characters that readers would have known well.

Usama also told a story about a Frank whom he had befriended, who wanted to take Usama’s son to visit Europe:

"My brother, I am leaving for my country. I want you to send your son (my son, who was with me was fourteen years old) with me to my country, where he can observe the knights and observe reason and chivalry. When he returns, he will be like a truly rational man.' And so there fell upon my ears words that would never come from a truly rational head!” (Book of Contemplation, pg. 144)

Usama basically said “thanks but no thanks” and gave a lame excuse (the boy’s grandmother loved him so much she could never let him go). Maybe this knight wasn’t real either but the sentiment was real: what could anyone possibly learn in backwards Europe?