Actually, whether it was a mosque or a church or a Wicca circle, it doesn't matter.
Send some 40mm their way (or whatever that thing was shooting).
Disturbing? Perhaps. Wrong? Perhaps. Civilized? Its war, civilization is defined by the winner. Next!
What do you do if your enemy, knowing you wont bomb a mosque, starts hiding.. umm.. in mosques?
Duma: Its unavoidable. Economic ties make "ignoring" other nation's be suicidal. Imagine for a moment the UN had not "mobilized" for the Gulf War. Iraq wouldve had a huge influx of oil money, which very probably wouldve ended up in their biochem/nuke program. Then what do you do? When they begin to export said stuff or use it on their neighbors... what can you do? In the long run you end up facing Iraq armed with WMD's AND no fear or regrets to use them screwing up the whole region because .. umm.. I dunno, they need lebensbraum or some other lame excuse to pull the trigger and conquer.