I don't want to use the word 'hate', because that's a very strong word. People throw that word around a bit too much. I hope my uses on this blog and in real life have really shown the passion someone has for something, negative in this instance. Let's just say we're talking about anime you loved but now loathe.
There are any number of reasons that this could happen. It doesn't make you a bad person by any means, so don't feel bad if you're in this situation! These transitions always have a chance of taking place as you go about your daily life. The world changes around us, and our tastes can change as well. Sometimes it happens without us even realizing it!
What reasons could their be for loving and anime and then despising it? Well, I think being extremely young when first viewing and then being more mature when watching again is a good cause. There's also the situation where you love an anime so much that you overplay it, and then you slowly start disliking a show that you were once head-over-heels for. This kind of stuff sneaks up on you, so be careful!
Can you name any anime features that you lost your passion for? Now you own a bunch of DVDs for a show you don't even want to watch! No worries though, because one day you might come full circle! You can't live your life with extremes 100% of the time. You'll probably find yourself in a happy medium someday!