Maybe it's not a purely cultural clash at all:

Afgan security forces worry about fratricidal brothers-in-arms

While NATO soldiers worry whether an Afghan partner might turn from an ally to a lethal foe, Afghan soldier Sayed Rahim says he's afraid his own comrades at a small outpost in eastern Paktika province will kill him.

"There are some soldiers who have Taliban war songs on their cellphones," Rahim said. "Do we do our duty, or should we watch out for these guys who will kill us one day?"

While successive attacks by rogue Afghan security forces against NATO allies worry Western commanders, less-known incidents of Afghan-on-Afghan violence within the security forces point to Taliban infiltration nearer to home.

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Personal grievances, battle stress, and domestic problems are behind more attacks than Taliban sympathies, according to NATO forces, who put the number of incidents by Islamic militant infiltrators this year in single digits.
The NATO coalition says a similar number of Afghan troops and police have died at the hands of their own compatriots.

"I can't really sleep. Soldiers don't trust one another very much. When I go to sleep I fear someone will shoot me dead," said Rahmatullah, a comrade of Rahim's near the Pakistan border, through which insurgents cross with reinforcements and material.

"We are also very fearful of food and night guards but what can we do? We are soldiers and have to do the job," the 24-year-old said in a province where an Afghan policeman this month drugged nine colleagues and shot them dead as they slept ...