It speaks nothing of the culture. We're safe.
You have to be aware that you are browsing an Internet - and while answers are generally accepted and encouraged by Community, these might still be lacking, wrong or misleading.
You can't help it.
However, you can always edit the question - so if you've spotted the mistake, correct it, improving the answer. The point of SE is to provide Q&A format of popular questions(and less popular too), so that whenever you encounter a problem, you can find compact solution, and solution is kind of public - you can edit it to improve, provide additional insight, or update, if such need arises.
Yet you specify the very root cause of the problem - people who are looking for an answer are usually people, who don't know the answer! Therefore, they might not see the mistake(especially this one, which could be considered relatively small, depending on context).
Note that this is inevitable in every source of knowledge - if you read academic papers, there are often some errors in there - some books contain wrong information too - blog posts, YouTube videos - mistakes are everywhere.
So we're good. The answer wasn't providing the shell script that wiped out your disc, it most likely couldn't affect anyone in a harmful way - so the worst that could happen is that the answer didn't work. And while it's sad to see upvoted and popular answer turn out to be wrong, in the end of the day we focus on our mission - improve it, and continue providing quality content to the users.
PS. Also note that as the Michael said, the system worked - and it worked well, actually. Compare this to the scandal I've recently learned about, where some physicist falsified data to provide (false) evidence to his theory. Now his work lasted for a bit longer than a question, he also received few awards for his work, until it was discovered to be a fraud. As I said - you can never be sure - but we are fortunate to have a community where providing false answers isn't profitable for both sides.