There are people who haven't read any SK since Carrie. Also, as mentioned above there are a lot of literary snobs out there. I have recommended SK books like Blaze and FDNS to people and while I may not have converted any to actual fandom I did succeed in changing opinions. If people don't want to know what they're missing, there's nothing you can do.
Also, most times people who are prejudiced this way against SK have only ever seen a few movies.
Asking them "what about The Green Mile" is always a hoot.
....I hereby present "Snooki"...
I think that horror in general gets a bad bad wrap. I was in my local large chain book store the other day and was looking at the rather large Sai King selection they have, and I could feel the eyes of the other patrons drilling holes into my head. Maybe it was my somewhat overactive imagination, but it was odd.