Totally, it's a lot deeper than a lot understand. Hell even wikifags etc have a lot of it wrong, like with the whole Nana (#7) situation.
Why hadn't Nana attacked anyone? It's not clearly stated but not hard to figure out once you grasp the themes the series followed.
She's been in the facility since birth - thus hadn't been abused by the outside world. Yes she was "tested" constantly (which they state was akin to torture) but it was done by machines not humans, so she never made the association. Instead to her humans were the ones that came to clean the blood off & feed her. They tend to get it wrong because Mariko (#35) was also in the facility from birth, but there's a difference - she never had any human contact other than being spoken to through a speaker by her foster mother.
Who she kills the moment she's set free
Basically she went insane, whereas Nana kept her sanity by seeing Kurama as her father - so she endured everything thinking it would make him proud.
That of course leads to her losing her arms & legs trying to restrain the much stronger Lucy just to make her father proud.
And just to make things worse for Nana she not only finds out that Kurama wasn't her father, she discovers that Mariko (who had tried to kill her) was the real daughter then has to watch her "father" die. Seeing her walk home afterwards is gutting.
Simply put, everything happened due to abuse & persecution. Excluding #7 & #35 all the other living Diclonius had endured the outside world & ended up hating humans because of what happened to them.
Even the so called happy ending doesn't feel it when you know everything they all went through. There's a lingering feeling from it all.
Kurama's a whole other kettle of fish.
He's not the bad guy or a bad person...