I don't think you need counterexamples, because your base argument is faulty. Food full of formaldyhde only causes harm as the product of human usage, i.e. someone eating it, regulation aims to make it impossible for such a situation to arise. For a less extreme but no less real example, just look at the regulation of raw milk in much of the world.
Elsewhere in the thread you have touched on firearm regulation; it's worth noting that amongst states with the capacity to do so, it is really only the US that abdicates its responsibility to regulate firearms, with predictably tragic consequences (though, as with everything in the US, that varies state to state etc.)
Your example is flawed because the harm is obvious and palpable. Not to mention food in most countries must disclose ingredients that are used. Take alcohol which is known to be poisonous. Do you support its banning: yes or no?
Food should be regulated because as you mentioned it is consumed and is a vector for obvious harm. In addition to that due to the fact that food is comprised of chemicals, it is difficult to ascertain the quality of food once prepared without consumption.
Banning AI is like banning books. Useless. Information will spread either way. It'll just do so elsewhere.
Elsewhere in the thread you have touched on firearm regulation; it's worth noting that amongst states with the capacity to do so, it is really only the US that abdicates its responsibility to regulate firearms, with predictably tragic consequences (though, as with everything in the US, that varies state to state etc.)