Working as a senior practitioner in CAMHS we get 60% referrals for behaviour and yes I'll be honest I do get fed up with the same old same old over and over again, not least because it makes the job boring and frutrating.
However, I would NEVER refer to nay f my families as scum of the Earth, they come from areas of high social deprivation, community fragmentation, they've been in care themselves, experinced domestic abuse, have LD themselves or and this is a big one, undiagnosed, ongoing PND that has affected the attachment with their child.
Sometimes we do have to be quite direct in our communication with them but it's about empathising and reaching a shared formulation of the childs problems. And with kids who're old enough to understand I'll be direct with them too about how undesirable their behaviour is!
ADHD and ASD exist with all sorts of shades of grey in between, it's overly simplistic to say "it's all down to bad parenting". I've seen families with 2 children adopted from 2 separate families, excellent parenting, one an angel, one very "challenging" there's all sorts of other factors like genetics, inherent temperament etc. that influence a child emotions and behaviour.
As for teachers, well there's good ones and bad ones all stuck in a difficult system. I communicate with teachers all the time and for every one that's kind, empathic and creative there's one who's horribly judgmental and downright unprofessional, unfortunate but true.