Knives don't talk to you and don't reinforce ideas you throw at them. Not everyone can legally buy a gun. Manufacturers don't get sued because their product's users had full control over what they were doing.

AI chatbots entertain more or less any idea. Want them to be your therapist, romantic partner or some kind of authority figure? They'll certainly pretend to be one without question, and that is dangerous. Especially as people who'd ask for such things are already in a vulnerable state.