The US policy following WWII to is that it does not target Civilian population centers, even with nukes, nor does it strike or target purely civilian industry or infrastructure. Each and every target approved is accessed for collateral damage estimates (how many civilians it will kill) vs the importance and priority of the target. Can intelligence estimates be wrong or based on false data, sure, happens quite often, but that does not mean that collateral damage was not calculated, just that when we got there afterwards, what we thought was there wasn't. Cultural centers, religious centers and hospitals are also protected, but if the enemy actually places military forces adjacent to them or in them, then they become legitimate targets. I cannot say all (I haven't been in every one), but most command teams that make decisions on bombing a target has a team member from legal to assess the legality of each target and whether they meet policy for collateral damage.
Now, in Iran, whom we certainly do not want to acheive nuclear weapons, we can put pressure on them to stop development (this has not even showed the least sign of actually working) or we can destroy those facilities prior to them acheiving their goal. That means bombing them. Due to where their facilities are located, it may not, in fact it is very doubtful, that the facilities and research can be destroyed by anything less than a deep penetrating nuclear weapon. Personally, I favor the invasion route over that, but not everyone does and some just want to believe we could do it with only conventional bombing. Should we chose to employ the nuclear option, we would consider the civilian population in the area and areas that would be affected. But, in the balance of things, if the whole of the Population of Iran were to become collateral damage, my assessment is that it is an acceptable level to prevent them from obtaining nuclear weapons.
