The trouble with the now increasingly common assertion that "There is no terrorism. There is only war." is that by legitimizing the deliberate infliction of maximum civilian casualties by the least powerful side in a conflict as a normal tactic of war; one cannot logically avoid legitimizing the deliberate infliction of maximum civilian casualties by the other, usually vastly more powerful side in the same conflict since this too becomes "the normal conduct of war."
Such a choice was, admittedly, tempting after school children were simply massacred in Soweto, but only because the white South African government that gunned down those children probably couldn't function without keeping most of it's black labor force alive - but precisely parallel arguments are harder to make in more modern cases.
Surely "There is no terrorism" is a less attractive political stance if it means that Israel gets carte blanche to see just how much of the Palestinian population it can kill if it exerts itself to the absolute utmost against the helpless civilian population of Palestine which hates it and considers itself at war with Israel - since the answer is probably "everybody." These aren't rules of war worth having.
Yet if deliberately setting out to cause the maximum number of civilian casualties one possibly can to the other side is perfectly excusable for nations whose names begin with "P", why then, it is perfectly excusable by nations whose names begin with "I" as well, since that is now "simply a normal operation of war" And it's hard to argue that Hamas is determined to cause far less havoc than it possibly could. Not with a straight face.
I don't relish this supposedly "new thought" as a way of “leveling the playing field” (pardon that pun) - since it is a return to WW II British Air Commander "Bomber Harris"'s ethic of indiscriminately killing Germans in night-time bombing raids. He at least had the very thin excuses that his poorly protected bombers couldn't effectively attack industrial targets in daylight raids, and that indiscriminate bombing would very slightly limit German war production by killing at least some workers along with the hundreds of thousands of elderly, children, and those infirm German citizens the Nazis hadn't already systematically exterminated themselves. But surely those excuses look quite thin in hindsight. British and Canadian night-time bombing (the Americans performed much more accurate daylight raids) wasn't then, and shouldn't be considered now, a legitimate tactic of war.
I'd rather not go back to that sort ethic or rule of war, thanks very much, despite the fact I know that it's the victors who tend to make the rules, that irregular wars do exist, that American Revolutionaries in the South successfully used executions and terror tactics to discourage Southern loyalists from joining up with British troops, and that partisans in WW II fought Nazism as "terrorists" since their other choice was to become (literal) slave labor for the Nazis.
True, if "nothing counts as terrorism" this would vastly shorten modern conflicts, particularly now that we have much less inexpensive thermonuclear weapons which are good for little except killing civilians. And true, once upon a time genocide wasn't a sideline but the often the very reason one went to war. But let's not go backward. Let's draw a line - if we can - that makes causing civilian casualties to those we don't like less desirable than causing military casualties or economic damage. Please. Some must lose their lives but do we all have to lose our souls?