As the graph shows, in every country, ISIS is unpopular, by huge margins (and I find it interesting that according to the same survey, attitudes vary more from country to country and between religions; but I’m not sure that’s important right now).
But there’s low, and then there’s low. I wouldn’t drink water that was “only” 1% arsenic (the EPA limit is a million times smaller than that), and if there were “only” a 1% chance of crashing every time I got on the Beltway, I’d likely be dead within a year. So there’s small and then there’s small.
If the KKK enjoyed the same level of popularity in Alabama as ISIS does in Turkey, above, it wouldn’t be reported as “KKK only has minority support”. It would be reported as “One in 13 Alabamans still supports KKK”.
So I’d like to see some figures for comparison: how popular is ISIS compared to, say, the Lord’s Resistance Army, or Nazis, or the Tutsi army? Maybe they have comparable levels of popularity, and the double-digit favorability numbers are statistical artifacts. And in fact, it seems that the fact that its popularity varies more from country to country, than from religion to religion within the same country, points at this explanation.
But my fear is that ISIS really does enjoy insufficiently-low popularity.