I think it's his style that they just can't compute. They're so used to having people give a clean, polished, scripted and rehearsed automaton response, written for them by speech writers, they can't fathom Trump's loose, laid back, relaxed and confident style. When they then have to put that into context their brains start short circuiting. And hey, it also helps if the media frame things in a certain way and help everyone along the path to the desired opinion, which they even have done here in the UK with the rolling news line that suggests he was practically telling people to shoot up with disinfectant like a junkie!