A shrewed politician he is this mr.lieberman. He knew that his proposed law will cause an uproar ( especially if its true that this was part of coalation agreement). His mind is already set on new elections. The postbibi time. He knows how to play ball and will earn brownie points.
If a terriorist shot dead the driver of a bus full of schoolchildren, what incentive would he have for releasing the children, knowing that he would be executed for killing the driver? In any event terrorists on a suicide mission would not be deterred by the death sentence which I believe would be counter productive.
But not just for terrorists, bring it back for rapists, child molesters and sex offenders - they are all scum and I for one, don't want to think that my hard-earned money is going towards giving them a comfortable life in prison. Plus, it's a very good deterrent - terrorists want to go out in a blaze of glory - not be executed by an Israeli.