I really think this is an instant when an artist's personality is rubbing the public the wrong way. You could say Mariah fans just hate her because she publically dissed her. But I think her attitude keeps a lot of people from embracing her. She's not someone you root for because she's kind of a snarky twit. Even Whitney was able to maintain some likability throughout her climb to the top. Christina comes off as a know it all who's better than everyone else. Even going so far as to put a rude diss of one of her producers on record (that's just a no-no). So while people may support some of her singles, it's tougher to support her career, because she's established that she doesn't really need anyone. The unoriginally doesn't help either.
Even her "shout outs" to her fans seem fake, contrived and totally ripped off from Mariah.