Why hate the Charmed Ones?
Because they are a bunch of beautyful but brainless females, typical for the modern age, who stumble through the events, surviving mostly on luck and seldom on talent. Even if they discover some knowledge or learn something, usually in the next episode everything is forgotten again.
Each of them has certain very ugly character traits, but most people don't even notice it, because apparantly beauty and a few pathetic speeches about doing the right thing is enough to mask the rotten inside.