If you read his manifesto in its entirety, you might rethink the “mental illness” diagnosis. It was not written by a crazy person. It was written by an enraged narcissist. No hint of delusion.
Would you also suggest that the apologists for the Third Reich who justified why the Final Solution had to be carried out were “mentally ill?” Doubt it. No one denies their agency. They were the authors and the perpetrators. We are more apt to correctly call them evil.
The Nazis hated Jews; this kid hated blonde girls and the guys who got to date them. The manifesto lays out, in perfectly cogent prose, why he hated them and what he was going to do to exact revenge. And he did it. Not on the scale he imagined, but he wasn’t delusional.
He was evil, not mentally ill.
Maybe you should try reading it. I read it and the person who wrote it is entirely delusional. If you actually read it, you will see the person did not even know what was going on around him. I never said one can't be mentally ill and evil. The shame is the parents knew that this kid wasn't right, but they never took him to get help.
Hitler was evil. But I have yet to hear of one person who doesn't think he was mentally ill.
You really need to actually read it. This person was extremely narcissistic, but also hugely delusional. His idea that these women hated him was entirely in his mind. His deranged ideas did not reflect reality. He even projects his delusional beliefs onto his childhood, but a rational person can see right though it. And it's obvious his parents were treating him in a certain way that he can't see through, because of his problems.