The fact that people need to see something evil before comprehending it says a lot about the lack of thinking skills in our nation. (thanks government schools!) It is quite true that it took the beheading of two people on video for many people to recognize the evil of ISIS. This despite reports of thousands of dead and dreadful attacks on Christians, especially Christian girls. It’s pathetic that society needs visual evidence of evil in order to comprehend it.
No, it says something about how the human brain works. There’s a reason we have so many tired old cliches that revolve around putting things in front of our eyes (see is believing, the show me state, a picture is worth a thousand words, etc etc), because our brain pays the most attention to the input from our eyes. It’s why we make visual models for things. It’s why so many languages have involved pictographs. It’s why people learn where buttons are but not hotkeys. We can conceptualize a lot of stuff, but nothing impacts the brain like stuff that goes through the visual cortex, in fact one of our primary forms of conceptualization is visualization. Railing against us for that is like railing against us for being bipedal, it’s the nature of what a human being is, and you have the exact same “problem”.