You have to take it as a given that other people exist, that you aren’t the only one thinking. If you’re not familiar with solipsism, you probably are somewhat confused. Some think that self is the only thing that can be verified. I’m assuming from interactions with other people and scanning of the brain, that other people do think. Therefore, they have a perception of self. Since self is the most important thing, even in others, destroying “self” is wrong. Killing is wrong because it ends thought and a sense of self.