Remember that everyone starts out incompetent. They ask dumb questions, and in some cases entitled newbies expect the experts to bend over backwards for them. But one thing that's nice is that a lot of questions have been answered before by patient experts.
Say there's a guy on the Ubuntu forums who asks the following question:
"Hey, how do I change my desktop resolution?"
An asshole answer is "Fucking Google it, idiot. It's not hard."
A decent answer is, "Here's a link to the answer. In the future, I suggest Googling your issue. You don't have to wait for us to answer it! Often, questions have been asked and answered before. We're here if you get stuck, though."
This has a few benefits. The first (obvious) benefit is that the newbie doesn't immediately think "Wow. What a dick, I was just asking a simple question."
The second benefit is that future newbies who Google the same question get a link to the answer.
Of course, there are lost causes (Where's the Start button? This isn't like Windows at all. I don't like it) and asshole newbies who simply refuse to try to learn anything by themselves, (Ok, you answered my question on desktop resolution. How do I change my desktop background?) but I think these people are the exception rather than the norm. And they can be dealt with in a way that is constructive rather than crass and uncouth.
Fortunately, you can easily killfile people in mailing lists, and doing so quickly (i.e. after one wrong post) helped me greatly.