The tone of the parents "in comparison with" others. I am not arguing that they were good or poor parents, but I think it is arrogant to assume they were completely ignorant.
They were talking about well after the physical addiction aspects would have subsided. Their issue was that they could not stay off of the drugs, beyond just the issues immediately following quitting.
I don't doubt for a second that the parents are disingenuous or self deluded.
I just believe that most parents, looking back at their children when they were young, would say 'they were such happy children'.
I do not believe that 'a happy childhood' in any way correlates with individuals likelihood of using/getting hooked on drugs - or their difficulty in 'getting off drugs'.
Opioid addicts in particular commonly indicate that once they are 'fully hooked' - that the drug stops become a thing of aspiration, rather, they need to take it to 'just feel normal' - and that without it, it's painful. This is the body's reaction to the drug. Being addicted to heroin sets a 'new baseline' for your bodies production of serotonin, dopamine etc. etc. which is unpleasant, and to feel normal, one needs ever more heroin uptake.
In a much smaller way - a similar thing happens with nicotine: the 'mini high' from smoking goes away after a while, at which point, without a nicotine hit - you feel uncomfortable. Getting the 'hit' reverts you merely to a relatively normal state.
They were talking about well after the physical addiction aspects would have subsided. Their issue was that they could not stay off of the drugs, beyond just the issues immediately following quitting.