You have to think in bigger terms here. If you destroy mecca, they have the backup site of medina. What needs to happen is this: tell the muslim world that the next terror attack on not just the U.S., but ANY nation, will be met with swift action by taking out both mecca and medina. Both sites will be destroyed and or nuked. That way, they can't fulfill a holy tenant of theirs that they have to go to mecca or medina once in their life.