That looks to me like a monstrous reluctance to comply with an important health and safety rule.
There were already several states in Europe which required compulsory vaccination before 1810 a few decades after it was developed. I think it seemed like a no-brainer to most at least slightly educated people in the 19th century (after all everyone back then had grown up seeing loads of people around them dying from all kinds of nowadays easily preventable diseases).
It's not so far from people fearing that COVID vaccines were full of microchips to control your brains, or that it was all a mass sterilization campaign organized by the deep state or whatever.
It's on the level of "you made a choice, alone, purely for the benefit of your family, not much socialist nanny state going on now."
There's plenty to discuss and even argue about across ideological lines. Unless it's straw-men all the way down when there becomes no point, which seems a shame to me.
Maybe next time phrase the thing more along the lines of:
"How do libertarians view such market regulation success?"
Yes but they are not necessarily able to clearly explain how can that be prevented from happening without the ‘nanny state’. Which I assume what the comment above was implying, instead of explicitly supporting poisoning food.
Even the most ardent libertarian at most believes that maybe 90% of the population can be 'protected' by various, non-govermental, systems to a sufficient degree, but there will always be some fraction, in this case tumeric eaters, that slowly get lead poisoned regardless.
How can this be prevented without a nanny state?
Libertarians in general, do not believe in the legalisation of violence which is orthogonal to the nanny state. Same as if someone were to randomly put arsenic in your food. That understood how do you deal with it? It's your right to knowingly consume poison in full knowledge of what it is and what it does to you OR you are prevented from doing so because, when you have full knowledge, you will make the wrong decision deciding arsenic is tastier or whatever. Noting also there exist compromises between those two (eg you can do whatever to yourself, but it's made harder - with differing views on how good or bad such policy is). All of those /can/ prevent _unwitting_ lead poisoning. Which polict is best, according to what criteria and at what necessary cost in trade off is something on which reasonable people can disagree, and can be discussed productively and in good faith.
But clearly not here today.