you want to tell israel not to over-react, but the fact is that this is different. i grasp that hamas thinks it's retaliating for however many years of indiscriminate bombing, but what did it expect the response to be? remember that dumb kid that picked a fight with the bully and got his nose broken?
what hamas has done is take away the generic response, which is severely harming their own cause. hamas clearly broadcast that it intends to drive israel into the sea and will if it can; a proportionate response would now be to completely obliterate hamas. there's nothing disproportionate about an attack designed to permanently dismantle hamas, at this point.
i would support a wholesale liquidation of hamas as an organization, and i hope this is what they end up doing rather than aimlessly punishing civilians. if they can capture the leadership alive and try them, all the better, but just killing everybody who's ever made a decision for hamas in the last ten years would be a proportionate response and difficult to criticize.
israel has total superiority in all theatres and over all potential conflict points. they can and should ensure that hamas ceases to exist, but they should be careful to avoid aimlessly killing civilians.