Why does Mr Knightley encourage Emma to invite the Coles but discourages her being friends with/setting up Harriet?
Essentially, Mr Knightley seems to want the Coles included in society where Emma doesn't ("Emma did not want to be classed with the Mrs. Eltons, the Mrs. Perrys, and the Mrs. Coles, who would force themselves anywhere;" "The Coles were very respectable in their way, but they ought to be taught that it was not for them to arrange the terms on which the superior families would visit them. This lesson, she very much feared, they would receive only from herself; she had little hope of Mr. Knightley, none of Mr. Weston.") because they are from trade and not gentility like herself/Bateses/Jane Fairfax/Westons/etc. Whereas Mr Knightley seems to thinkt hey should be treated as equalish parts of their society.
But then with Harriet, Mr Knightley's issue is that she is probably a decently wealthy girl from trade, whereas Emma thinks she must be gentility, which he warns Emma about. He doesn't like Emma's elevation of her, because from his perspective, it goes against the class order, whereas he is doing a similar thing with the Coles, not considering himself that much above them. He says,"I am not to be talked out of my dislike of Harriet Smith"
I am just having trouble understanding this discrepancy. With Harriet, Knightley seems to want Emma to learn that she is not superior, she is not part of their class, and is in fact lower than Mr Martin. Whereas with the Coles he seems to think they should be permitted into their society, and that Emma should learn the same.
Essentially, what am I missing here? Is Mr Knightley for or against a small erosion of the class system or does he think it should be strictly maintained?