Rules of Engagement?

As the war in Gaza rages on and the peace talks have all but evaporated, the Israeli Defense Forces have been air-distributing leaflets warning--urging, really--Gazan civilians to evacuate their homes, and cut off all contact with Hamas.

The New York Times ran a story today that quoted Fred Abrahams, a senior researcher at Human Rights Watch, as saying "you can't drop a 500-pound bomb in an area crowded with civilians."  Abrahams also discussed how the emerging humanitarian crisis stems from Israel's unwillingness to battle within the confines of the internationally recognized rules of "distinction and proportionality."  

While I understand that "rules of engagement" are necessary for conflicts (especially with the constantly evolving and increasingly complex urban-guerilla warfare tactics) I think that Abrahams has jumped the gun here.  The conflict is difficult and unusually critical for civilians as the Gazan borders are closed, but the strong response by the Israelis is as pin-pointed as possible.  Hamas militants are hiding in underground bunkers, and more difficult still, are unabashedly mixing with civilians while under fire; in some cases, Hamas elements have been witnessed using civilians as shields.

I think that the "rules of engagement" should be changed.  The rules of war have changed, after all, and that change necessitates a switch in the philosophy of humane conduct under conflict. 

Is it wrong to call the Israeli response inhumane when Israeli civilians had been suffering under Hamas attacks in the southern region?  Is it wrong to call Hamas inhumane for fighting a war in tunnels and amongst the cities, thereby increasing civilian casualties?  The lines have blurred, and instead of increasing the finger-pointing, it's time for diplomatic leaders to reconsider humane action in 21st century warfare.