Iraq: So called "holy shrines" used to attack coalition troops

From CNN

KUFA, Iraq (CNN) -- U.S. soldiers killed at least 16 suspected insurgents early Sunday and found a large cache of weapons at a mosque during an operation in the city of Kufa, a stronghold of radical Shiite cleric Muqtada al-Sadr and his Mehdi Army militia, military officials said.

[...]

Aided by Iraqi civil defense forces, troops found AK-47s, rocket-propelled grenades, rocket launchers and more than 2,000 rounds of ammunition, officials said. Some of the weapons were stashed in the mosque's minaret.

If these places are so "holy" why do they allow weapons to be stored there?