Malice is fueled by grief.
While it is never stated, it is highly implied that the reason so many monsters are malicious is because of the tragic circumstances that happened in their lives. For instance, Toriel and Asgore likely became malicious after losing both of their children, and Napstablook probably became malicious because he was ditched by his cousin.A souless being, can't be corrupted
In the main game, we know that Flowey's soulless nature makes him incapable of feeling love, but what if it also means he can't feel any negative emotions like hate? The reason why this version of Flowey isn't like the one we are used to is because he is constantly surrounded by people who hate their lives.