This answer is dangerously unsafe. Is it valid to flag such a post as needing moderator attention?
Since we don't actually have moderators yet (just admins), I don't know that flagging it would do you much good at this point. Even when we do elect moderators, I don't think I would flag it; downvote and comment as necessary.
I liken it to a Stack Overflow answer with a dangerous security flaw. I have enough faith in the community to sort these issues out without moderator intervention. If it becomes a serious problem, we can revisit the discussion.
The best thing you can do is to downvote the question to show you shouldn't do what is suggested. In most cases, it can be hard to draw the line of what is good/bad behavior and I don't think that it should be a moderators job to judge the contents of a post.
After all the up/down vote system is made for something like this.
This could compare this on stackoverflow when people write a post with code that will introduce bugs or security issues. We downvote those answers and comment why you should definitely not do as the posted, we don't flag them for moderators.
How about a big red disclaimer? Something like "The answers to this question are potentially unsafe, and you are responsible for all safety research before following any advice." Maybe even put it in the notification dropdown for badges. Also, we could only show the disclaimer on questions that are tagged "food-safety", or potentially another special tag.
I obviously don't know any legal stuff about this, but maybe it'd at least make people think twice before trying something.