Why did Harry hate Draco at first sight?

[romuluslupin1]

No: HPFGUIDX 112654

I was reading an oldish post re: why did DM want to make friends 
with HP and I have a question of my own. Why did Harry hate Draco at 
first sight? He specifically thinks that he hates this boy more than 
Dudley. Why? Granted, Draco is rather obnoxious, a snob and a half, 
whatever. At the time Dudley was surely worse than a boy he'd met 
for 5 minutes? Dudley's been tormenting him for 11 years, for Pete's 
sake. 

Can some learned mind help me solve this puzzle?

Romulus Lupin