I've been thinking about this. I don't think that it so much that people want to be lied to, it is that people want sympathy and/or validation.
There are essentially two types of posters who start threads here - those seeking information, and those seeking validation.
As I am not quite as nice as crashbb,

I will cite some examples. Today someone started a thread asking about what to do regarding ID as her wallet was stolen. She was provided with information, links to websites, real life examples, and a little humour. She thanked everyone, and hopefully will put the information to good use. That is the type of poster who seeks information, and who is usually (but not always) grateful for the assistance. Sadly, there are also those seeking information who pose a question, receive a series of responses, and never even have the courtesy to say thank you for the information, even when some of us did quite a bit of research on their behalf.
Then we have the poster who comes seeking validation, usually for behaviour which they generally already know is against the airline policy or social norms. These are typically the people asking if they can bring on a too large/too many carry ons, or pack water in their suitcase, or bring PlayDough on the plane, etc. Depending on how they pose the question, they receive a variety of responses. As the question inherently asks how to break the rules or how to do something which negatively impacts others, they may also hear suggestions for how to do things differently. Typically these are the threads which become playground matches, full of name calling and finger pointing.
And that I frankly do not understand. If a very seasoned traveller told me something such as, well, for example, 'Packing pickled herring and liquer filled chocolate together in your suitcase is not the best idea, as you may find that herring juice seeps into your chocolate and that you end up with a permanent stench in your suitcase', I would most likely thank them for the advice. If another poster came along and gave me a link to where I could buy my chocolate online, I think that I would thank them as well.
Much of the behaviour that posters wish to have validated impacts other people, and is thus inconsiderate behaviour, even if they did not realise it. When their proposed actions impact others around them, I see nothing wrong with providing alternative solutions, and explaining exactly why that behaviour is antisocial. (Yes, Mom, I realise that you don't like my use of that term, but if you can suggest a better translation for ,Asozial' I will take the recommendation)
As someone else has pointed out, this is a discussion board with an open exchange of idea. It is not a validation board or a personal blog. Posters cannot expect to only read responses which agree with them.
I for one have always been humble enough to appreciate the information I gained by reading over at
www.flyertalk.com and on other websites. By doing so, I have been able to enjoy my years of travel far more than if I blundered along with a lack of information. Yet many people seem to be resistant to learning, or seem to be ready to pick a fight. I meet those people quite often in airports, and have seen them here as well.
Airline travel really isn't as bad as people here make it out to be, or as Duds and I discuss, DISworld differs greatly from RealWorld. (Either that, or some of us just travel in a parallel universe to the rest of you)