I disagree with the quote. Hurt people hurt. You think Jeffrey Dahlmer wasn't damaged as a kid? Look how he turned out.
Probably a bit of both. Damaged people either turn out to be complete psychopaths like @Wrecky or really nice dudes like in your quote.
I'm pretty weird so I used to worry about being a psycho or whatever, but then I realised I cry when watching The Iron Giant. Wrecky though, she started masturbating at the end of Marley and Me.