People are too distracted by his actions to be willing to consider his motivations. It’s understandable, but such blindness keeps people from understanding the motivations of some important historical figures. Killing people is unethical by every standard and immoral by most. But bad actions are not necessarily irrational. The man wrote about his motivations. His manifesto is worth a read.
Discussion
Most people think it’s unethical and crazy thing to do, because they don’t see the consequences of not doing so. Sometimes you have to pay very big prices to avoid very bad outcomes. If one can’t see the outcome, he can’t understand the cost.
I don’t think what he did was right, I still cannot fully agree with his method. And it’s not up to me to judge whether it was right. But I absolutely think he had such a through understanding of social psychology, political identity, and technology’s effect on human as a whole.