oomis1105: what your doing is bringing negative proof, which is no proof at all. a mother who abuses her child or is indiffernet to them is not normal, and not something to bring a proof. if a mother only has adoptive or step children, then all is equal, and no harm can be seen. when a step-parent also has biological children, which is in most cases, then the love they are showing their own children will never be the same as their step/adoptive children, no matter what. if she treats her natural kids like garbage, more so the non-biological ones.
negative proofs, like the ones you brought, are never used in research for that exact reason, they are negative, as they negate the norm. a rapist can technically be a better parent then a non rapist, if the rapist only rapes adult males or females, and dodes on children. if the non rapist is emotionally abusive, they will do more damage. but this is abnormal and cannot be used as proof that rapists make good parents.