Try this mental exercise. If I say to you 'bananas', 'oranges', 'apples', 'plums', 'grapes', you can get hold of the differences, right? OK, now see what you make of this: 'bowl of fruit'. Did you have trouble? I'm guessing not. Now, here's another exercise: 'imprisoned without trial'; 'tortured'; 'forcibly evicted from their homes'; 'brutalized for participating in public protest'; 'fired from their jobs for belonging to a trade union'. Again, any difficulty seeing that these are distinct cases? Surely not. But if I spoke of them all as the 'injustices' perpetrated by some regime or other, your knees would not, I hope, go all wobbly.
There are several different strands in the objection made to the war on terror - both the thing itself and the phrase. Pretty well all of them are unpersuasive, in my own view, but I won't go over the whole collection again. One that is worth special mockery is the notion that to speak of a war on terror as a general phenomenon is bad because... the referent is composed of particularities. You'll be able to disentangle this strand of argument from a leader in today's Guardian. David Cameron is taken to task there for falling foul of the injunction 'don't talk about global wars'. He is praised for acknowledging the existence of 'different insurgent groups in north Africa with local leaderships and agendas, not all suffused with the same ideology'. The failures of al-Qaida are, too, due to its thinking of its cause in global terms. It has been weakened by 'local specificity'. And so forth.
One might think that the Second World War - or the First, or any war - had been just a great shapeless flom, with no distinguishable parts, or countries, phases, interests, strategies, diplomatic, political and military aspects, regional and local specificities. One might think this, if thought came into it.
There are certain clear common features in the war on terror, one of them suggested by the last word of its much-lamented name, others to do with the illiberal nature of those organizations making use of terror to try and achieve their aims, another to do with the military 'component' in the waging of it by democratic countries.