I think such liability as "someone talks to the chatbot, gets wrong reply and poisons themselves" could be disclaimer by such conditions: "Our chat is unsuitable to discuss topics X, Y and Z. If you choose to discuss them anyway you're doing it at your own risk.

But this would require an admission of limitations of the technology.

Do people sue Google if search links to a page that has misleading info that results in someone taking a wrong drug? Nope.

Do we sue the browser maker when the info on a given Web page is malicious? Also no.

So, I don't understand why we treat chatbot providers any different. Everyone should be expected not to believe a word they say without corroboration.