It's not that mosques are sacred. It's that Muslims get upset if non-Muslims attack a mosque. Screw 'em
I understand the ROE in Iraq permit firing on a mosque if Ally Forces are fired upon from the mosque. That is the middle of the road compromise for now. I don’t think that proscription was in place during WWII. If I understand those who fought that war in Europe, they generally tried not to bomb where it didn’t help, but that, on the ground, they did not wait to be fired upon from a church. They did what they had to do. I think God or Allah would excuse some rubble to prevent something far worse.