Ok, so what happens then? After Israel kills every single Hamas member, what then? The next wave of people who had their families killed will just retaliate against Israel. What then?
If they're too dumb to understand when they're beat, it isn't a problem for the US. But that risks sweet Saudi monies, so it will never happen.
No matter what, there will always be some evil and some violence. Trying to reduce anything to zero always makes the cure worse than the disease.