@Saki: I kinda doubt my response is in response to what you're thinking about. It sounds like what you have in mind is people who actively trash shows, and that's not what I'm talking about below.
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There's a difference between hating something and deciding it's not worth your time because you'll never get those hours of your life back.
Most American TV falls in the latter category for me, but I don't "hate" all of them. In fact, there are almost certainly some good shows I'm missing out on as a result. But I choose not to because in my experience, most of them will probably be so dumb they'll make my brain cells start committing suicide.
In the same way, there are anime that I choose not to watch because they have traits that in my experience are associated with shows that were worse than a waste of time. Massive fanservice, fans who think that it's TEH AEWSUMEST EVAR, and fans who denigrate anyone who doesn't share their high opinion of it are all on that list of traits.
I don't "hate" One Piece, or hentai, or a lot of other shows. I can't hate them, because I don't know enough about them to hate them. I just don't want to watch them. Maybe it's my loss, but I don't.