‘The people who suffer most at the hands of Daesh should decide what they are called’.

Also, if you read the whole article, it does explain that it's a bit more than just calling them something they don't like. I tried finding a short quote that sums it up, be instead I'll paste a wall of text:

And so if the word is basically 'ISIS', but in Arabic, why are the people it describes in such a fury about it? Because they hear it, quite rightly, as a challenge to their legitimacy: a dismissal of their aspirations to define Islamic practice, to be 'a state for all Muslims’ and – crucially – as a refusal to acknowledge and address them as such. They want to be addressed as exactly what they claim to be, by people so in awe of them that they use the pompous, long and delusional name created by the group, not some funny-sounding made-up word. And here is the very simple key point that has been overlooked in all the anglophone press coverage I’ve seen: in Arabic, acronyms are not anything like as widely used as they are in English, and so arabophones are not as used to hearing them as anglophones are. Thus, the creation and use of a title that stands out as a nonsense neologism for an organisation like this one is inherently funny, disrespectful, and ultimately threatening of the organisation’s status. Khaled al-Haj Salih, the Syrian activist who coined the term back in 2013, says that initially even many of his fellow activists, resisting Daesh alongside him, were shocked by the idea of an Arabic acronym, and he had to justify it to them by referencing the tradition of acronyms being used as names by Palestinian organisations (such as Fatah). So saturated in acronyms are we in English that we struggle to imagine this, but it’s true.

All of this means that the name lends itself well to satire, and for the arabophones trying to resist Daesh, humour and satire are essential weapons in their nightmarish struggle. But the satirical weight of the word as a weapon, in the hands of the Syrian activists who have hewn it from the rock of their nightmare reality, does not just consist of the weirdness of acronyms. As well as being an acronym, it is also only one letter different from the word 'daes داعس' , meaning someone or something that crushes or tramples. Of course that doesn’t mean, as many articles have claimed, that 'daesh' is 'another conjugation' of the verb ‘to crush or trample’, nor that that is 'a rough translation of one of the words in the acronym' – it’s simply one letter different from this other word. Imagine if the acronym of 'Islamic State in Iraq and Syria' spelt out ‘S.H.I.D’ in English: activists and critics would certainly seize the opportunity to refer to the organisation as ‘shit’ – but I think it’s safe to say that no serious foreign media outlet would claim that 'shit' was another conjugation of the verb 'shid', nor a rough translation of it. Of course, that analogy is an unfair one, given the hegemonic global linguistic position of English, not to mention the heightened currency of scatological words; but there is a serious point to be made here about the anglophone media’s tendency to give up before it’s begun understanding non-European languages.

And obviously understanding things outside of English, and explaining them to each other via our (social)media hive mind is hugely important on many levels: in the broadest sense, it allows us to attempt to take our place as global citizens, and feeds our connection to other humans on planet Earth. Sadly, the story of the word 'Daesh' is neither the only nor even the worst example of anglophone media failing us in this regard. But there’s something specifically important in this particular story which is being overlooked as a result of all the lazy journalism around it: the use of this word is part of a multi-pronged, diverse range of efforts by Arabs and Muslims to reject the terrorists’ linguistic posturing, their pseudo-classical use of Arabic, their claims to Quranic authority and an absolute foundation in sacred scripture, as reflected in their pompous name. This ridiculous claim has of course been masterfully and witheringly deconstructed at the Islamic level, but at the secular level, satire is a crucial weapon in the fight against these maniacs: there is a fertile tradition of Syrian and satire as not only defiance but coping strategy, and which has been quite under-reported. In satirical Arabic media (and conversation) various diminutives of the word have also gone viral – elegantly diminishing their subject, belittling them, patronising and relegating them to a zone beyond any formal naming in a single sweep.