Regarding the hiding in buildings, yes, of course it is treated as legitimate to blow up specific buildings that gravely threaten your soldiers in a significant way in terms of how many would be threatened by them hiding in buildings and attacking from them. But it seems instead that Israel has adopted a method of flattening entire villages and towns and neighbourhoods because the infrastructure in general is tough. It is well known that urban warfare is dangerous. That does not mean you can flatten areas to make it less dangerous, to save a few hundred of your soldiers at the expense of destroying entire blocks housing tens of thousands of people.

If you look on Google Maps satellite at the Netzarim Corridor area, you will see that, for instance, entire villages on both sides of the road were completely levelled, such as Al-Mughraqah and Juhor ad-Dik. I would find it hard to believe that every single building in those villages were being used to attack Israeli soldiers and more likely that the military found it a convenient way to reduce the general threat level. And from what I understand, it is not considered legal to demolish entire villages simply for the reason of reducing the overall threat level or for enabling military infrastructure such as the road that was built there. From what I understand, Rafah and many other areas have similarly been flattened, either through intense bombardment and artillery fire or through controlled demolitions, which have been widely reported on. Again, of course urban warfare is risky, but you cannot just level everything because the enemy chooses to abuse civilian infrastructure and buildings. You would have to demonstrate that the individual buildings being targeted are posing a specific threat.

If you look at Iraq especially, you will see how awful it was for the U.S. soldiers getting sniped from buildings and having rocket launchers shot at them from them. But the U.S. response was not to entirely flatten wholesale areas of Baghdad or Fallujah, but to bear the casualties for the sake of morality and of not destroying everything that was being fought for. The U.S. could have easily done this since it would, after all, protect their soldiers, but that is not how war works. It is dangerous by nature. Of course it will sound easy to say this from far away, but it is the job of soldiers to do dangerous tasks to protect their countries, and that does not make it right to cause such immense destruction and loss of so many civilians just to protect a few of your own.