I think it will come as no shock to anyone that i disagree. 
I hope you'll do me the courtesy of actually reading the whole response before assuming what it says.
This thread perfectly demonstrates why I disagree with your premise....
Not all questions are created equally and not all questions SHOULD be answered. If someone is asking how to do something that will negatively impact their system in a way that they have not considered, you do that person a disservice by answering their question. Furthermore, if you know that it will negatively impact their system and you don't point that out, you have done harm to that person by your inaction.
Seinfeld fans know what I'm talking about.....criminal indifference. 
While that was taken to a comedic extreme, the principal is still applicable. If someone is asking a question similar to the one linked above, what should someone reading it do in that case? Let them learn it on their own? In that specific case, I was not the first to read it, nor was I the first to respond, both of which scared me. All of these people could read that post and not point out the danger? What if someone had gotten injured because the guy installed a smartswitch on a garbage disposal? And I'd done nothing to prevent it? While obviously not legally culpable, I would have held myself morally culpable for not doing what little I could to try and prevent it.
Personally, if I'm trying to do something that isn't going to work or there's a much easier way to do it, PLEASE tell me. I like avoiding unnecessary work and headaches.
By saying that something is a bad idea, you're not calling the person who came up with it "stupid" or insulting them. Brilliant people come up with amazing craptastic ideas all the time! That doesn't make them any less brilliant. Or mean that the other 10 ideas they came up with today aren't great. It just means that this particular idea is bad. In other words, someone saying "That's not a good idea" should not be equated with "You're stupid."
IMHO, people need to take things a little less personal. If someone is taking the time to point out that what you want to do isn't going to work the way you hope/think it is, rather than just assume they're doing it for nefarious reasons, why not assume that they're doing it to help you? You can only hear what someone says through the veil of your own prejudices. If you assume someone is saying something for a particular reason, I guarantee, you'll find evidence to justify it. Rather than jump up and down on that person, why not give them the benefit of the doubt?
