Draco and Harry are the ying and the yang. If it wasn’t for Harry, Draco would be the “Teen Dream Jock” who rules the school and body slams the av nerds and computer geeks into lockers because they can. And not only can they, half they school wishes they could do it, too, and envies the ones that do. No one wants to be a bottom feeder, and so most people want there to be someone below them in the social order. The ones on the very bottom just want to disappear like Mia in “The Princess Diaries.” When James and Sirius were fifteen, they ruled the school. Their word was law, and Snape was so far down the social ladder that contact with him would give you “cooties,” and you would be fair game with him. Half the school wants to either torment Snape with James because Snape "deserves" it, or they are so afraid that they could end up just like Snape that they say nothing. “Mean Girls” goes into the dynamic of what it means to be popular because there is always someone prettier, smarter, and more ruthless than you to take your place. Draco’s world is the male version of “Mean Girls” and Harry arriving at school with his built-in celebrity upsets that balance of power. Rather like having some famous TV Star kid going to the school and the whole social order has to be rearrange to accommodate them. Those with the most to start have the most to lose.
Harry arrives at the school after ten years of having his power binded because any demonstration of it would be severely punished. Suddenly it is not only not bound but he is encouraged to use it. Both his parents were talented, and he obviously inherited from them in full measure, but he also inherited from Voldemort on the night Voldemort tried to kill him. Even Dumbledore does not know what Harry got from Voldemort that night, although given the prophecy, he suspects, so that seems to be a major reason why Dumbledore put Harry with Dursleys and not a wizarding family. Another Voldemort, no one needed. Draco puts moral limits on Harry. Harry sees Draco’s excesses and is appalled, and will do anything to not be like Draco. We have already seen evidence that if Harry’s negative side was unleashed, he would make Draco look like nothing. I think Draco reinforces Harry’s compassion and humanity. Without Draco, Harry could easily become the next Tom Riddle, believing that anyone less powerful than himself is insignificant and unworthy of consideration. I think he saw in James, things he sees in himself that he is frightened of becoming, which is why he needed Sirius to tell him that the memory was not true, and James was not, and he cannot become, a selfish monster. I think James and Sirius were far more like Fred and George than the heartless monsters that Snape remembers.
Balance is maintained as long as each of them keeps the other in check.
I remember sistermagpie has referred to Draco as Harry's moral touchstone ('Am I as arrogant as Malfoy?' 'I don't want anything Malfoy thinks is good'), and that's what the girl is saying here too. -On a sidenote, I would say Harry 'uses' Dudley the same way too, behaviors that resemble that of Dudley are big no-no's, eg. bullying and being spoilt- She goes on to illustrate just how normal Draco and James really are in an ordinary school setting, which I agree. The only significant difference I think, will be that Draco essentially has a KKK fanatic for a father, and that because of the upcoming war, he will be forced to choose whether to join force with a bunch of terrorists at a relatively young age. (Such things of course don't happen to ordinary teenagers, jocks or not.) HP readers thus view what Draco says and does as having implications much more grave than they truly are. Like, Draco calling Hermione a mudblood is not the same as say somebody in my high school calling a fellow student a 'Chink', because there seems to be a larger chance Draco will actually do something to follow through his words? But haven't we also seen in both POA and GOF, that Draco did not physically hurt nor let someone physically hurt Hermione when he got just such chance to? *shrugs*