I haven't had time to participate fully in the Group Read, but I've enjoyed lurking on the board and this discussion is very interesting to me.

Perhaps the anser might be found in the opening passage to chapter 3:
Mr. Woodhouse...liked very much to have his friends come and see him; and from various united causes...he could command the visits of his own little circle, in a great measure as he liked. He had not much intercourse with any families beyond that circle; his horror of late hours and large dinner-parties made him unfit for any acquaintance, but such as would visit him on his own terms. ...Not unfrequently, through Emma's persuasion, he had some of the chosen and the best to dine with him...

I don't think anyone consciously taught Emma to be so condescending about the lower classes; no one she looks up to would have done so. I think she has taken her cue from Mr. Woodhouse, except that she has added a rather supercilious edge to it. He doesn't meet with other people because any kind of change makes him nervous; she might have decided for herself, in a fit of teenage haughtiness, that there must be other reasons he leaves out certain people from Highbury. It's just that she hasn't given it much thought since then, or had reason to wonder whether these other folks have merit.