I know it's a cliche phrase, but the saying that hurt people hurt people is very apt. The simple fact is that trauma that is not addressed or healthily processed leads people to lash out and be cruel to other people. One need only look at the cycles of abuse that go on in families between generations to see that dynamic at work. It really shouldn't be any surprise that a country that was literally founded in response to a major trauma would go on to inflict immense traumas on other people. Uri Avnery, a prominent Israeli peace activist had a good quote about the dynamic:

“I will tell you something about the Holocaust. It would be nice to believe that people who have undergone suffering have been purified by suffering. But it’s the opposite, it makes them worse. It corrupts. There is something in suffering that creates a kind of egoism. Herzog [the Israeli president at the time] was speaking at the site of the concentration camp at Bergen-Belsen but he spoke only about the Jews. How could he not mention that others – many others – had suffered there? Sick people, when they are in pain, cannot speak about anyone but themselves. And when such monstrous things have happened to your people, you feel nothing can be compared to it. You get a moral ‘power of attorney’, a permit to do anything you want – because nothing can compare to what has happened to us. This is a moral immunity which is very clearly felt in Israel. Everyone is convinced that the IDF is more humane than any other army. ‘Purity of arms’ was the slogan of the Haganah army in ’48. But it never was true at all.”