Why does Killer Kane say that Grim and Gram poisoned Max?

Kenny “Killer” Kane is not saying that Grim and Gram poisoned Max with literal poison. Instead, Kenny “Killer” Kane is insisting that Grim and Gram have “poisoned [Max’s mind] against” Kane. Max’s dad keeps insisting that he “never killed anybody.” As a result, Kenny “Killer” Kane tries to convince Max that the reason for Max’s negative feelings towards Kane are a result of the “lies” told by Grim and Gram. Kenny “Killer” Kane keeps Max tied to a boiler in the basement of an old woman’s home nearby in order to continue convincing Max that the “lies” are not true. Kenny “Killer” Kane insists that the reason why Grim and Gram told Max the “lies” was simply to keep Max away from his real father. As readers, we know that Grim and Gram are Max's caretakers because they love him and because they want to protect him from Kenny “Killer” Kane who truly is a murderer.