Justin Bieber is perhaps the most hated and loved at the same time. CoedMagazine ranked him 7th as the most popular WOMAN online. Not the first ones to make a Bieber joke, intentionally or otherwise.
Nathan Yau at FlowingData created the reference poster above that highlights the most disliked videos on YouTube of all time.
The video Baby featuring Ludacris has over one million dislikes. Most likely the first on youtube with such a high number of dislikes. He still has several videos with millions of likes as well, so the hating isn't too out of proportion still.