I'm neutral about Sasuke. I do not like him but I do not hate him either. He's someone I wouldn't root for as much as I would for someone like Madara, Itachi, or one of my other favorites.. but I wouldn't ignore or bash about him either. I think he's rather important in my opinion, but simply not on my favorite list.
Though I think people don't like Sasuke due to his fans is because (from what I've seen thus far, not all) but a good majority of Sasuke fans act immature. Though, I see nothing wrong with that. No matter what character you are a fan of, there will be that chunk of the fans who act childish and spam '*enter their fav here* > your fav' and/or troll those who do not agree with them. Not only that, but for some, it can make the one they say is greater than your favorite look bad due to the immature fans.
I hope I answered your question a little bit.