There is no "explanation" for their behaviour other than (a) cowardice, or (b) hatred of non-muslims.
Actually there is, if you are willing to learn it.......I repeat, I am not making excuses for Islam, hell, I don't much like the religion, and have studied the 'Quran a bit......it is sorely in need of both a reformation, and a ecumenical hierarchy, both of which would improve the faith immensely, unify it, and make it far more understandable to non-muslims. From a scriptural perspective, with the exception of the Sura, it is nearly identical to Judaism........
Unfortunately that is unlikely to happen as the faith currently exists, as they are still fighting between themselves as to which sect's leaders are or are not direct descendants of the prophet.
The majority of Muslims are not cowards........we have many in our own military services........and agree with or or not, it takes a bit of dedication to strap several kilos of Semtex around your waist, and die for the cause.......
Based on my time in Saudi, most Muslims don't hate westerners either........they are suspicious of them, sometimes for good reason, and more importantly, most Muslims are ignorant of the world outside of their small sphere of exposure. As a group, education, (other than religious) is at best a low priority, and at worst, frowned upon within Islam........it is therefore not difficult to understand why they react as they do. Doesn't make it right from our perspective, but they are what they are.........
Were you to happen upon a remote Amazon tribe, their reaction to a westerner would be similiar.
doc