In fact, it is my understanding that the Koran allows Muslims engaging in a jihad to change their appearance and practice the behaviors they find reprehensible in able to assimilate unnoticed into the culture they are fighting against.
And I'd like to know where you got this "understanding" from. Islam in itself was a cultural revolution when it first emerged; so why would the Muslims try to assimilate into the culture that they were being persecuted and killed for breaking from?
Perhaps you were mistaken by passages that make exceptions for that which is forbidden: "He has forbidden you carrion, blood, and the flesh of swine; also any flesh that is consecrated other than in the name of God. But whoever is driven by necessity, intending neither to sin, nor to transgress, shall incur no guilt" (Qur'an 2:173). That means you're not sending us to hell when you follow Black Jack Pershing's suggestions to dunk your ammo in pig's blood and fat and then bury us in the pig's entrails. But it doesn't mean we can start eating pork and drinking alcohol just to pretend to fit in.
But while we're at it, let's take a look at how much less violent God's chosen people were at God's request in the Bible:
"They warred against Midian, as YAHWEH commanded Moses, and killed every male. They killed the kings of Midian ... And the people of Israel took captive the women of Midian and their little ones; and they took as booty all their cattle, their flocks, and all their goods. All their cities in the places where they dwelt, and all their encampments, they burned with fire." (Numbers 31:7)
"And Joshua mowed down Amalek and his people with the edge of the sword. And YAHWEH said to Moses, 'Write this as a memorial in a book and recite it in the ears of Joshua, that I will utterly blot out the remembrance of Amalek from under heaven. A hand upon the banner of YAHWEH! YAHWEH will be at war with Amalek for all generations.'" (Exodus 17:13)
"David struck the land, and saved neither man nor woman alive, and took away the sheep, and the oxen, and the donkeys, and the camels, and the clothing; and he returned, and came to Achish. Achish said, Against whom have you made a raid today? David said, Against the South of Judah, and against the South of the Jerahmeelites, and against the South of the Kenites.
David saved neither man nor woman alive, to bring them to Gath, saying, Lest they should tell of us, saying, So did David, and so has been his manner all the while he has lived in the country of the Philistines." (1 Samuel 27)
I'm not trying to say that I'm out to be against all Jews and Christians just because David and Joshua seemed to build their place in history from a large pile of corpses, but merely that all the Abrahamic religions found it necessary to take up the sword at some point.