From my understanding the poll was done by the editors that work there. It wasn't a public survey. I don't think it is a reflection of Japan. I also wouldn't say they are haters or hate Ayu. It sounds to me they don't like her voice, too many negative media coverage/scandals, she isn't young anymore, just a general decline in image and quality of output. Most of what is mentioned is pretty shallow basically.
Ayu is always ranking as most liked or most hated it seems.