She certainly is creepy there. I mean, I even agree with her that jinxes can obviously be useful when used defensely. But that's not what she's disagreeing with. She's disagreeing with the idea that she can't give her own jinxes a euphamistic name that makes them not jinxes. And that, of course, ties into everything Hermione does in that book that's so distasteful. It's not, to me, that she sometimes chooses to be ruthless, it's that she pretends that's not what she's doing. I mean, she's even in denial there: "I think they can be very useful when they're used defensively..." as if the DA would never use a jinx other than defensively. They use them anytime they want to and call it defense.