Perhaps I'm misreading why this should be off-topic. It seems not only on topic but exemplary in defining how not to treat guns and gives an opportunity to explain why.
With respect to matters of safety and idiocy, I would want a site that doesn't close these things as off topic. Many questions on cooking for instance involve addressing food-safety. I agree with Jengu's response: Scary question to delete. If someone wanted to learn how to do this, I would want them to find the overwhelming screams of "DON'T DO IT!"
If I were just 5% dumber than I currently am, I might go ask on Seasoned Advice, "hey, is it okay to eat my fried chicken off the cutting board that I prepared the raw chicken on to save on clean-up?" In this case, I might be too dumb to even realize the potential risks. If this question is considered off-topic and closed, or not a good example of a question, then it sets a precedent for not allowing for many teachable situations.
I know in some cases off topic questions are answered and closed, but I think this should not be one of those scenarios. The problem with this approach is that then, someone looking for topically similar information won't likely come across this question, or may be confused as to why it is closed. It should be left open so that it is a relevant search result.
We should see the value in situations where someone asks a question, and not only gets an answer the behavior in check, but further explains the problems associated with the risks inherent to the behavior. I would think that a Firearm stack would take every opportunity to explain not just that, yes in fact that is a bad idea, but furthermore, *here's why...*.
Those are the really rewarding and valuable questions/answers.