The problem with giving the "friend" the benefit of the doubt is that it placates them, but leaves the OP feeling like shit. The OP has every right to be upset about being used like this, and to ask the friend why they behaved the way they did.

Maybe the friend didn't realize they were being an ass, or maybe they did. But IMO there is no excuse for rudeness, and chalking it up to POSSIBLE social anxiety just puts all the blame on the anxiety and not the person themselves. Having anxiety does not excuse dickish behavior.