Mecca.
You know the terrorists don't give a fig or a grape about Mecca. They operate under the cover of Islam, but they are not Muslim. Besides that, Muslims don't practice idolatry, so wouldn't be religiously attached to any particular place. They would be upset, probably annoyed, but they would continue on in their muslimhood. But keep making the suggestion; there may be a prize for the 100,000th who makes the suggestion.