I'd prefer if Israel just blatantly just said "We kill them because they are the enemy and our enemy".
Because I hate it when people try to justify injustice. Just let your true colours be known to the people who support.

And when people who say Hamas brainwashed them, I say to them who is Hamas? what power do they have against Israel, which owns an advanced military, nuclear weapons and America as its ally (in it's pockets likely). There is nothing stopping Israel from killing their leaders so what do they need them for? they even threatened them over and over again. But they need a scapegoat next time they kill Palestinians.