Lots of people don't read sci-fi, not just Oprah. That still doesn't mean anything she reads is trash. I myself don't read much romance, but there are a few authors in that genre who I do enjoy, and if my mother (who does read romances) recommends a book to me, I would consider it before I decide to read or not. Sometimes, I may read the book, sometimes I may decide it will not be to my tastes. I don't dismiss all suggestions just because they are coming from that one person.
I agree with what Bob said in the other thread. You are just as much of a 'lemming' for avoiding a book just because Oprah suggested it as you are for reading it just because Oprah said so
I could understand (maybe) the sentiment if this was an Oprah publishing company where she was getting it from, or if Oprah was getting paid to push specific books. But many of these authors were out there before Oprah ever found them, so I see nothing 'wrong' with Oprah reading them, liking them and giving their sales a boost and getting people reading by suggesting books she herself has enjoyed.