AI generated content should be treated like any other content. If it's good you upvote it, if it's bad you downvote it, if it doesn't answer the question you delete it, if it's an off-topic question you close it.
AI might sometimes provide useful content, and will probably provide some wrong answers as well. So will regular users.
We should not police the tools that participants use to construct questions and answers. Some tools are better than others, but there are probably none that are perfect. We don't have rules that you can't use Wikipedia even though it might contain incorrect information; we don't have rules that you can't use a translation of a book that might be flawed; we don't have rules that you can't ask your friend a question and post their answer.
The only appropriate way to judge a post is by its content. An answer generated by AI might be a great answer. It shouldn't be deleted just because of its origin. A question generated by AI might be interesting, thought-provoking, and lead to answers that provide new insight on a topic. It shouldn't be deleted because it was created by AI.
Furthermore, there is usually no foolproof way to be sure if a post was generated by AI. By having a no-AI policy, we risk falsely identifying posts as AI content, and/or getting into protracted debates about a post's origins. Accusing users of such tactics may lead to unwanted drama, and discouragement of some participants.
As of now, we do not seem to have a problem of being inundated with heaps of bad AI posts. It is not such a big deal if there are a few posts here and there with AI-generated bad content. And if there is a particular user that continually posts such answers, they can be dealt with the same way any other user would be dealt with for similar infractions unrelated to AI.
Prohibiting AI generated answers sets a precedent in the realm of censorship. The site should be a place for free and open engagement with all people and all ideas that meet the site's scope. It is not a huge leap from deleting AI content to deleting content from sources we deem invalid, to deleting answers that contradict an author's statements, to eventually deleting anything we don't agree with.