Those replies often have a great deal of truth in them, regarding genes/upbringing.
It is well known the abused are far more likely to abuse.
What one experienced as a child is often passed on.
I have had psychiatrists tell me of their experiences in paediatric forensic psychiatry - for example, four year olds who literally try to kill them every time they try to see them, because the four year old child never had a normal life.
Research has shown that babies that are adopted but who do not have a positive safe bonding relationship by (I think) six months of age turn out very differently to babies adopted who have had a safe bonding relationship by six months of age.
Genes and the environment do shape us and our actions to a surprisingly large extent.