The disproportionate response (DR) argument is all over the left-wing Web, from Prospect.org to the disreputable wingnut sites. The DR is an attempt to restrain Israel in a situation, conventional warfare, where they have the advantage. "Proportionality" is never defined. No examples of such are ever provided aside from the cheap and easy cry to "only hit Hezbollah targets."
Hezbollah committed an act of war. The leader of Hezbollah declared "open war". Under the old rules of war, this is justification for Israel to destroy Hezbollah utterly. But under the DR argument Israel has to be restrained to only cause a 'proportionate' amount of damage. Hezbollah indescriminately targets Israeli civilians. Israel bombs runways and roads and TV stations. Israel drops leaflets telling Lebanese to evacuate certain areas prior to attacks. Yet Israel is accused of disproportionality.
There are two kinds of disproportionality weasels. The first, the most simple minded, just count the casualties on each side and declare the side with the most dead to be the "victim" of the disproportional response. This argument display gross historical ignorance and a bizarre ethical system to say the least. Under this notion, Nazi Germany and Imperial Japan were the victims of disproportionate US response. Sad.
The other DR weasels are more clever. They argue that "Israel has not taken every precaution to avoid killing innocent civilians". Naturally Every Precaution can never be taken as the number of precautions included in 'Every' would be infinite. Israel's attempts to avoid hitting civilians, which are inevitably incomplete, are dismissed because "intent is not enough." Israel is described as "belligerent" and "eager for war." These DR weasels ignore Hezbollah's belligerence. Indeed Hezbollah is dismissed as mere terrorists, or downplayed as a Shia gang, all the better to portray Israel in a worse light for "going balistic" on the poor Lebanese.
If this new rhetorical weapon succeeds then it will be deployed later against the US. I can hear it now. "Iran only killed 10,000 Americans. You can't destroy an entire country. You can't wipe out an ancient civilization. You can't," they will whine. "That's a disproportionate response."