The reason that we all hate K-Fed is that we love Britney. Britney was not only a superstar pop-singer, but she was her own brand. She was a fat girl dying to get out perhaps, but she was definetly a brand that we knew and loved. Then comes in K-fed and he RUINS our favorite brand/singer and makes her this ugly fat trashy mess. We are pissed. We don't like the fact that he has done this and it seems like she is lost forever.
Also he seems to look like a weasel and his behavior is terrible. He seems to not be aware of this and I think the public would be more forgiving of him if he tried to change his image.