I mention this because on the bus home I was thinking of another example: "Chasing Amy." I love that movie. Love, love, love it. And if you just summarized the premise--lesbian falls in love with a man--you might wince, thinking they're going to do this whole redemption through heterosexuality story. But you can't watch the movie and reduce it to tripe and stereotypes, because the characters are complex, and because the movie meta-comments on itself and fractures any attempts to read it as that type of story.
To me, any work--TV ep, movie, book, whatever--has to work and earn some credibility when it comes to playing around with old stereotypes. And I don't think Smallville has.