The warriors of ISIS are proud to be terrorists and proud to be brutal. And learning this has made the Internet crusade to convince people to call them "Daesh" seem extra dumb.
Daesh is an acronym for the original name ISIS fought under before declaring their "caliphate" (a formal religious-led Islamic state) and, so the argument goes, they just hate it when you call them that. But from what I can tell, ISIS doesn't seem to care much about that themselves.
Which, of course, makes John Effin Kerry look even stupider than normal.