On the Percy/Arthur question, I'm completely on Percy's side. I think Arthur Weasley is a horrible father, and his behaviour towards Percy proves it. He willingly leaves the twins and Ginny bully Percy by every possibility they get without doing anything to prevent it, while Molly at least has the decency to yell at them. Just because Arthur isn't willing to sacrifice his screwed-up enjoyment of modifying people's memories for the good of his seven
children /meaning that he could get a better job if he wanted, but he just doesn't want to/ doesn't mean that Percy has to think the same way. I blame Percy only for his behaviour towards his mother, not his father.
I voted Ron on the Ginny/Ron issue. It was none of his business whom his sister was kissing and whether they were doing it in public or not. Even if she was screwing Dean in the middle of the school corridor, it still wouldn't have been his business. Yes, Ginny was out of line, but honestly, someone had to tell him what a jerk he was being. I just wish Hermione would've done it.
I agree on the Harry/Draco question - Harry has been living in the MW long enough to know that 'enemy' there means someone you wish more dead than alive.