It’s a cop out to avoid thinking
When someone kills a bunch of people or does something else horrible that normal people can’t understand, the natural reaction from many of us is to say “he was just crazy”.
But I don’t buy this. First of all, this attitude seems like a mental trick to avoid thinking about the rationality of what the person did, to avoid sympathy for the person and to distance yourself from them. Sure, many people are quote-unquote “crazy”, but we’re all crazy in some little way, and we all still have thoughts going through our brain and rationales for what we do, regardless of how unpopular or incorrect they may be.
I feel the concept of “they’re just crazy” instills unnecessary fear in people because it implies that there are people out there who have no rationale and simply do things blindly, like robots, and can’t be reasoned with. The concept is sort of the agnostic/atheist equivalent of “The devil made him do it.” This is counterproductive to actually dealing and communicating with these types of people. I believe this emotional distance, fear and stereotyping ultimately serves to make these “crazy” people even more crazy.