In a word, "nothing."
There's nothing wrong with Israel defending itself against rocket attacks launched from Gaza. Nothing. I have the right to defend myself, you have the right to defend yourself, Israel has the right to defend its people.
Does Israel's right to defend itself against terrorist rocket attacks from Gaza give it the right to respond with terrorist aerial bombardment of the Palestinians?
Most of the aerial bombs Israeli jets are dropping into the overcrowded neighbourhoods in Gaza are of the type depicted above. They're American designed, if not American built, and come in 500, 1,000 and 2,000 pound denominations. They're high-explosive bombs that generate not just shrapnel but incredibly lethal blast:
"Blast is caused by tremendous dynamic overpressures generated by the detonation of a high explosive. Complete (high order) detonation of high-explosives can generate pressures up to 700 tons per square inch and temperatures in the range of 3,000 to 4,500º prior to bomb case fragmentation. It is essential that the bomb casing remain intact long enough after the detonation sequence begins to contain the hot gases and achieve a high order explosion. A consideration when striking hardened targets is that deformation of the weapon casing or fuze may cause the warhead to dud or experience a low order detonation. Approximately half of the total energy generated will be used in swelling the bomb casing to 1.5 times its normal size prior to fragmenting and then imparting velocity to those fragments. The remainder of this energy is expended in compression of the air surrounding the bomb and is responsible for the blast effect. This effect is most desirable for attacking walls, collapsing roofs, and destroying or damaging machinery."
"...For purposes of the present discussion, however, let us concede that the bombs and missiles strike with all the accuracy claimed for them. What happens then? As described recently by Newhouse reporter David Wood, the 2000-pound JDAM “releases a crushing shock wave and showers jagged, white-hot metal fragments at supersonic speed, shattering concrete, shredding flesh, crushing cells, rupturing lungs, bursting sinus cavities and ripping away limbs in a maelstrom of destruction.” Hardly anyone survives within 120 meters of the blast, where pressures of several thousand pounds per square inch and 8,500-degree heat simply obliterate everything, human and material. Metal fragments are spewed nearly three-quarters of a mile, and bigger pieces may fly twice that far; no one within 365 meters can expect to remain unharmed, and persons up to 1000 meters or farther away from the point of impact may be harmed by flying fragments. Of course, the explosions also start fires over a wide area, which themselves may do vast damage, even to structures and people unharmed by the initial blast."
Aerial bombardment of residential areas is not a legitimate means of self-defence. Targeting a Hamas police headquarters in a built-up district is quite different than bombing a known site used by rocket launchers. Furthermore, police are considered civilians under the laws of war. But this doesn't hang on fine points about the culpability of any particular agent of the elected Hamas government. It's about the deliberate killing of innocents to avenge the deliberate killing of innocents.
As I've written many times before, we are all deemed to intend the logical consequences of our acts. That applies to you, to me and to governments. The logical consequences of aerial bombardment of residential areas include the deaths and maiming of innocents. This is terrorism.
So, it's not about whether you're pro-Palestine or pro-Israel. Even if you're pro-Israel you're backing a terrorist state. Aerial bombardment of civilian areas is rank butchery, plain and simple. It has nothing to do with self-defence and everything to do with retaliatory terrorism. The fact that Israel is our ally changes nothing.