I think that the response depends a lot on the flow of the conversation. If I was chatting with someone about a show we both liked and someone else felt the need to jump in with "I can't stand that show!", I'd be taken aback and feel a bit attacked. If I asked someone what they thought of a show and they had the same response, I wouldn't feel the same way. My rule of thumb is that I don't jump into a conversation to say I hate something. (Unless the conversation is about how much people hate X.
) But I'll respond honestly if asked. I dislike the LOTR books, so I'm used to conversations on it going both ways.
Also, there are ways and ways to respond. I've definitely heard the "ugh, Twilight fans are vapid, shallow twits"-type response, which I think is rude and immediately downgrades the speaker in my perception. But "I don't care for the writing style" or "I didn't really like the portrayal of relationships
" is just a normal difference of opinion.