@Zhe compared the issue with medical questions. The reason medical questions are closed is because it is illegal to practice medicine without a licence in most places and people fear litigation.
Not because self diagnosis or self medication is inherently dangerous if one has the skills and knowledge. The issue is that the medical fraternity and increasingly homeland defence (or equivalent), with society tagging happily along, are happy to have the general population predominantly ignorant of medical and chemical minutiae lest they make mistakes or successes that cost lives.
There is no general law that prohibits discussion of chemistry or we could no longer prepare food or raise a cake. However there are various laws and restrictions on discussing various chemical processes in various locales. Nobody can know all the laws in all the locales and common sense suggests that SE is not the place to promote risky or antisocial behaviour but also not the place to police knowledge in favour of an incumbent nanny-state. Adding restrictions (and never removing them) will eventually lead to societal collapse because all personal freedoms have been lost. Mixing vinegar with baking soda outside of designated and licensed baking premises will otherwise eventually become illegal due to the danger of generating enough carbon dioxide to asphyxiate a cat, this road is not the one we should follow on SE as this road will also close down SE for good.
However as I wrote in another thread recently I am not in favour of eliminating questions that can be answered without other serious misgivings. SE is about preserving knowledge and a warning is better than prohibition. Prohibition has been tried before and found wanting.
Those who don't like the question can down vote teh question, answer with dire warnings and down vote any bad answers. They can even edit the question to make is less scary or dangerous sounding, to the limit of the collective censoring tolerance, but there is still little case for removing the question unless it is a direct call to illegal activity or impossible to improve. Chemistry follows impartial laws and not the political climate of human society.