"Nevertheless, coming from a mother, they are disconcerting and suggest disappointment ? anger even ? at the way he has turned out."
Would you believe it? This woman, this mother has the sheer effrontery to be disappointed that her son will never be able to lead a normal life and is putting the whole family at constant risk!!! The sheer brazenness of it!!! 
"While many parents and experts will testify to the prevalence of ADHD, others are sceptical, suggesting that it is merely an excuse for a lack of discipline and lazy parenting. "
Oh yes, absolutely. Parents who don't have children with ADHD are clearly the specialists on the existence of the condition. I don't believe in cerebral palsy. Never seen a sign of it in my children and they are beautifully disciplined, which just proves it. 
"Yet the timing of the diagnosis is curious. For years, Jenny and Dave had been rowing, until in 1997, after 13 years together, they divorced.
The following year, when the children were aged nine, eight and four, all three were diagnosed with ADHD.
Jenny will not entertain the possibility that her children?s problems were linked to her marriage break-up, even though this was suggested to her at the time."
And no kindly person has suggested to the journalist that maybe there is more than one way of marriage break-up relating to disability. 
"?I?m trying to get a business off the ground, teaching people to sew, but it?s not making money yet.?She sees putting Ryan into full-time residential care as the way forward. Such a move might be perceived by some as an attempt to offload the challenges of caring for Ryan on someone else, but she insists it?s the right thing for him."
Yeah, those mothers are all the same. When dd needed her knee seen to, I offloaded the challenges of caring for her onto a surgeon instead of getting busy with the kitchen knife. Some mothers are just feckless like that. 
"?I will be able to see Ryan all the time, but I will get a break.?
Whether her son will feel the same contentment at being separated from his mother is another matter."
I take it the journalist is home schooling her children then and never letting them out to spend time with others.
What I can't understand, OP, is where they get people like these journalists from. Imagine if one of our children grew up like that. We really would feel we had failed at parenting then, wouldn't we?