Spoken like someone who has never met an evil 11 year old. Or a moderately edgy 11 year old. ... Or someone with a good memory and/or long-running diary.

You state many things as facts about the world, as though they are simply obvious to everyone. What is your evidence? Why do you believe what you believe?

I learned the word rape when I was somewhere around 9, from a cousin who was only 3-4 years older, who casually inserted the rape and murder of our relatives into a game scenario once. So all I got was that rape==bad, probably violent thing that is distinct from but related to murder. So then I made a joke about it on a fieldtrip, and one of my friends got sufficiently uncomfortable to report it, which got my parents to tell me that ... "it's a very bad thing". Eventually, someone at school (I think it was the same one who reported but Idr) explained it to me.

The reporting-friend was not an asshole. He was responsible and also intelligent (we alternated years winning the science olympiad, it was a point of pride whenever I could best him at anything, etc). Other students were not so well-behaved or serious about such subjects. Though, I will grant that the sexual edginess I only started noticing at 12. If there was any the year before, I didn't notice well enough to remember. but 12-14-year-olds, including those still prepubescent, were talking about sex edgily like it was something new they'd just realized they could do, or something. Apply cultural shenanigans for wizard klansmen, and Draco pulling what he did at 11 is not at all unrealistic.

I've never met an 11-year-old with Draco's plottiness, but I've never met an 11-year-old who got manipulation lessons from Darth Vader their entire life, either.

As for Hermione, I'm not sure what specifically seems unrealistic about her, age-wise.