Anyone who thinks parenting practices -other than the most extreme- shape behavior should think twice and look at the evidence. The blank slate by Steven Pinker might be a good starting point.
There's plenty of evidence that the effects of parenting are generally smaller than we would like them to be, again with a few exceptions.
As you rightly point out extremes of Abuse and neglect have the most long lasting impacts on human development than nearly any other factor.
However even with those examples excluded, the amount of talking that a child is exposed to when in their developing years has significant impact on their long term development; see the "word gap" [1]. Not only that but nutritional environment (often based on parental choice) for the first 2-6 years has a massive impact on long term brain development [2].
So yes in fact parenting practices have a massive impact even when you exclude abuse and neglect.
Except that what many of us here would consider extreme are actually pretty common. Estimates for the prevalence of domestic violence and sexual abuse are difficult to measure accurately, but are conservatively > 10% in the population at large and much higher in the deprived communities which will be targeted by these laws.
Having spent significant time of my youth in a bad neighbourhood (with awesome, stable parents though), and having spent much of my later life with people on the edges of society, I can confirm this. It's reached a point where I'm shocked to not eventually hear some awful stories about childhood of these people.
From what I recall, Pinker makes no such assertion. Rather, he argues that we underestimate genetic effects and that while this is understandable from an ethical/political perspective, it is ultimately harmful.
In fact, I vaguely recall that on the issue of parenting he argued that genetics play a big role, but that so does parenting.
Basically, he's arguing that we factor in genetics more, not that we disregard parenting and social environment as a significant factor.
(but be sure to let me know if I'm wrong. It's been quite a while since I read The Blank Slate)
There's plenty of evidence that the effects of parenting are generally smaller than we would like them to be, again with a few exceptions.