True, which has been defined as when the mosque is being used for offensive operations against our troops, which nullifies its protection under the Geneva Convention. I don't consider that too restrictive. It becomes a legitimate military target at that point, and does not require anything resembling Presidential approval to be hit. In fact, the decision can be made by the troops in contact.
Don't discount the destructive ability of a 500lb bomb. It is more accurate than its 2000lb brother, and is more than capable of flattening a mud walled mosque. Plus, it has the added side affect of not flattening the friendly Marines within 1/2 mile of its impact point. Sure, 500lb bombs are the smallest we carry...but they are the weapon of choice for countless reasons that have nothing to do with PC.
Bottomline, I agree with your final statement with one editorial adjustment..."The next time we are fired upon from a mosque, two 500 pounders through the filthy dome should be the response. "