So you are saying those attacks didn't happen?
The methodology behind their data seems fairly reasonable to me. What's your evidence that they are fabricating attacks? What percentage are fabricated?
Usually people just glaze over when seeing the stats around Islamist terrorism because it doesn't fit their pre-packaged worldview. The only Islamist attacks they know about are the ones on CNN, so when you tell them hundreds of people are being murdered by this ideology all over the world on a month by month basis they find it hard to process.
In their mind the "alt-right" is just as big if not bigger of a threat because it's all they hear about in the media, and naturally deaths in third world countries just aren't worth worrying about.
Only a morally deficient psychopath could, after being presented with the true toll of the misery, death and destruction being meted out in the name of this one religion, then come out with statements like "all religions must be criticised equally".