There are 2 main aspects to this discussion, as far as I can see:
- Bad security model - security getting in the way
- Bad user model - not understanding what allowing access to a machine entails.
In the example of the linked question, you present a perfect case for 1 - the system security is causing you a significant delay when starting your machine, which would be a non-issue if you didn't have to interfere halfway through to satisfy some academic security requirement which isn't actually an issue for >50% of home users.
But also there's the problem of people allowing too much access to their machines - like sharing their whole disk with the world and allowing anyone to read and write anywhere, just so that they can copy files to it from work.
At the end of the day, I guess most, if not all of this, is really down to a bad security model - even if technically it's right, if the only thing a user can do to actually use a system is turn off security, then, at the very least, the user interface is wrong.
However, given that the vast majority of security models are wrong in some way and do cause issues, what do you do about it?
A lot of the time, the question's asked on forums are second degree questions, as opposed to first degree questions - for example, someone will ask how to enable worldwide sharing to their disk. If you directly answer that question for them, their machine will probably be totally compromised within a few minutes. If, however, you get them to ask the first order question "How do I share files between home and work", you might be able to give them a much safer answer.
Usually, this is the case - that people start to solve a problem using the tools they have, then hit a wall where the system doesn't behave as they want, and easiest way forward intellectually at that point is to break down that wall rather than back up a bit - hence the bad questions.
Equally, it doesn't help if someone says at the outset "How do I share files between work and home", and the answer comes back "don't be stupid, that's a security risk". Pointing out security implications is part of the answer, but the requirement still stands, if the question isn't answered properly, then how is anyone to know the security difference between sharing a single folder, non-suid, non-exec, fully audited, IP filtered and certificate controlled, vs just opening up the whole machine?
From what I've seen, SO is generally quite good at getting to the first-order questions. That's really the key of the whole thing, that and respecting the validity and requirement of these questions.