Honestly?
I hate them because they are so good, and have been our biggest threat over the years. No other team in history has challeneged our superiority as much as the Lakers, and no matter what people say, the team you hate the most is the one you fear the most.
They can never, and I mean NEVER, get as many championships as us, and whatever we have to do to prevent that, must be done without question.
The other stuff, like Kobe's sickening arrogance and ego, SV's attitude, Fish's dirty play, Jackson's air of superiority, Pau's llama face and nasty hair, Artest's moronic childish acts, their overly-obnoxious fans, those horrendous uniforms, endless flopping, the blatant preference from the league, all that stuff just adds to the hate and serves as additional excuses for the acrimony.
But the fact remains that they are our biggest threat, and in turn, that is why we hate them the most. Otherwise, they wouldn't be worth wasting the negative emotion on. Biggest competitor = biggest threat, biggest threat = biggest enemy, biggest enemy = most hatred.
Period.
PS - Lakers suck.