Moslems love face very much, just like asiatics. To the Japanese, they are very reluctant to criticize their warriors for slaughtering and raping across East Asia during WW2 because it is seen as being unfillal. So all references to bad deeds are either covered up, or put in very polite terms.
During my younger days, I discussed with moslems in real life about the contents of the Bible. One of the things they disliked about the Bible was its clear references to misdeeds of the "prophets" or Biblical characters. The moslems I talked to were shocked that the Bible would so blatantly talk about King David committing murder and adultery, or about Noah being seen sleeping naked. They felt it was very disrespectful towards the prophets and such verses should have been covered up or rephrased politely.
So, when we discuss King David, even Christians agree that King David committed murder and adultery, which was plain wrong. Yet, when we discuss about moslem muhammad or his companions, and questionable things he did, there's always a perfect, justifiable reason for what he did. And if you question further, you are guilty of apostasy, blasphemy or maybe even a zionist agent.
The pscyho-mechanics of it is pretty much like nearly everything else we do. We trade. We do and sacrifice in exchange for something else. In every other religion, people do good deeds, enforce self discipline in exchange for atonement of sin and entry into paradise. Most people think this is normal. Yet at the same breath, they dislike it when other people volunteer at PA in exchange for faster queues in popular primary schools. Even grassroots leaders like myself dislike such volunteers. We see them as hypocrites.
In the same light, I see people as following religious diets or doing good deeds just to please their god or because they fear for their soul as hypocrites. What sort of fucked up god will think good deeds out of fear of hell is the right attitude in life?