Those are the most serious allegations:
"The men and teenage boys were taken to a warehouse where they sat on a bare floor covered in scattered grains of rice. There they were beaten, interrogated and verbally abused. There was no sleep, and the grains of rice cut their skin as they sat there, undressed."
A man claims:
"Some people didn’t return from the torture sessions. We would hear their screams and then nothing.”
From what I read, it seems typical of counterinsurgency war.
A testimony is no proof but humiliation and torture is commonplace is counterinsurgency wars, whether systematic or an initiative of lower ranking soldiers operating on the ground, so it's not an extraordinary statement. And torture can obviously lead to death.
https://en.wikipedia.org/wiki/Counterinsurgency
Now I am going to argue something polemic and I am arguing it in the spirit of discussion. I'd love to read well argued counter-arguments :
However supportive of Israel one may be and how repulsed one should be by Hamas, I'd say that we should not fool ourselves in that the military operation in Gaza is Israel defending itself ("Israel's right to defend itself" is now a commonplace phrase) rather than avenging itself. You may think it is justified in doing so but it still is payback imho.
In my country's law, individual self-defense is defined as such :
1. It has to happen in the same time as the agression
2. Its only purpose is to defend against the agression
3. The defense has to be proportionate
It seems that so 1. is not met since once all the militants having trespassed having been killed, Israel was no more defending itself. and it's hard to believe that the civilian collateral damage is just defending either. I'd say the third criteria is met in so far as Hamas has rockets and automatic weapons.
Is that an unreasonable take ?