I have no idea how to parse this comment. Calling someone a "spastic" seems horrible. Kids in schoolyards looking to score points at the expense of the disabled are horrible. Assuming that a kid with ADHD is the victim of bad parenting seems like a terrible idea. Following your idea to its logical conclusion, it seems like we'd still be calling black people the n-word; after all, much of the use of that word in the first half of the 20th century was probably intended to be neutral.
It seems horrible now but it was the normal term at the time; even the charity was called the Spastics Society. And you only have that reaction because you've bought into the PC game.
But my point is, PC doesn't really work. Everyone "knows" what is really meant by any of the PC terms.
One day back in the 80s Blue Peter decided it was going to do something about discrimination against what were then known as "spastics" (I will use the term as it is historically correct). So they got someone on called Joey Deacon (see, I can still remember the name) to show that they were just normal people despite their physical condition.
It backfired spectacularly. The next day in the playground, "Joey" was the insult of choice. Now this may just be because kids are stupid and cruel but there is a lesson there: you can't do social engineering by clumsy attempts to manipulate language. It just doesn't work. So (for example) nowadays when we hear that a kid has ADHD, everyone just rolls their eyes and knows perfectly well that is just the PC way to say "bad parenting".