I'm not sure of the Lord Peter Wimsey example. Sayers tends to be pretty harsh on middle-class people, especially pseudo-intellectuals, but the actual lower-class people tend to be competent, sensible, and pleasant. (Examples: Bunter, Mrs. Ruddle, Officer Kirk.)

When is Applejack shown to be dumber than the other characters? (Especially Pinkie Pie, but that's not really the point.) If we distinguish between lack of intelligence and just being uncultured, that is.

CMT is really bad about it. For a show that claims to be dedicated to the rural blue collar working class, they seam to show the most stereotypical hics out of all the networks.