When you are asked for an unwanted advice....

Ever been in a situation when someone asks for your advice, but doesn't really want it? They ask just for the sake of it, or to make themselves feel as if its a very big decision they are going to make. Don't know what goes on in their minds when they do such a thing, but it generally irritates the hell out of the poor unwanted advisor.
Its worst when you can see that the person doesn't really want it. You neither can flip them off nor do you feel like saying what you really think about it.  When you do try to flip them off by telling them what they want to hear from you, they get offended and tell you that you don't care about them and that you should respect the fact that they are asking for your advice. Well, listening to such words, you relent, and you start telling them what you really feel- which obviously is miles away from what they want to hear. Quite patently, they get offended anyway and tell you that they are sorry that they ever asked your opinion. And that's when you really get pissed off. If you are a quiet sort or are not in the mood to make a big issue out of it, you keep quiet and either brush it off or keep it to yourself and work yourself up about it. On the other hand, if you are in no mood to be complacent, you give them a piece of your mind, and the whole issue somehow becomes your fault; because they were the ones who first came to you for advice ( which, according to them, was a sign of respect for your opinions) and you, instead of giving them a good one, are rowing about their motives.
So, what is the way to deal with such situations, when no matter you open your mouth, or not, you get in a pickle anyway???