I know how you feel (I think).
It's all about two things from what I've learned: 1) Over-sensitivity, 2) Comfort Zone.
The reason a lot with SAD think people are *******s is that we're usually way too sensitive, putting meaning in things that are just part of the "normal" social world, that others don't see. Because we're this sensitive, we retreat into our heads after some initial bombardments, and suddenly we're detached from the world, watching it on distance. Then we think it's "their world", and we create our own safety zone, for example our house, or the closest people around us.
Now... Unless one is happy in this situation, one has to try to combat it. I've been lucky enough to find friends and a girlfriend, that I can keep in my comfort zone. But I still have a problem in relation to the outside world, and how I interpret it emotionally. And when I for example bring friends/girlfriend "outside" with me, it messes me up inside and can become very confusing. What I'm trying to say is that there are two parts here: Everyone needs other people, but even though you find friends to fit in your comfort zone, I don't think anyone can be happy until they understand and accept their position as a sensitive person in the outside world, and try to place emotions that are relevant another place than oversensitive emotions.
It's a fine balance accepting One's oversensitivity and loving it, side by side with struggling to create more harmony between yourself and the world. But I believe that if One can only be comfortable within the safety zone, it creates a wall that just grows bigger and bigger and in the end One can't be happy like that IMO. Just comfortable. The fact that everyone in here IS actually here, means that we all aknowledge that we need others, but the PC is indeed a safety zone for communication where everything's kept at distance.