All children deserve a good standard of education. I believe passionately that educating young people is the most important tool we have for making the world a better place. Of course, part of that is understanding that not everybody is NT, not everyone has an easy home life, and either or both of those things could cause some children to misbehave. We can make the world a fairer place by making appropriate allowances for those differences so that those children have the best chance they can of achieving their potential.
However, I don't think it's "pearl clutching" to be concerned about the impact of disruptive behaviour on other children. Their education matters just as much. If there is a class of 30 children and one or more are persistently disruptive then some of those disrupted children might be naturally bright/studious and/or have parents who have the time, ability and inclination to tutor them at home to help them reach their potential. Some parents might pay for extra tuition or send their child to private school instead. Sadly, there may well be other children in that class who have difficulties at home but who fall under the radar because their behaviour is better.
But I would imagine that the majority of children, depending on the area, have parents who don't have spare money for tutors, can't afford private education, and don't have the time, ability or inclination (or a combination of these) to help their children catch up on things they should be learning at school. My own, very loving and nice parents, fit into that category. They both worked, had 3 children and weren't particularly academic. The last thing they wanted to do after working, cooking and clearing up was to sit three different aged kids down, work out what they were each missing out on in 6/7 hours of potentially disrupted classes that day and then try and teach it to them. How could they possibly manage that? How much harder would that be for lone parents, parents for whom English is a second language, parents who are working opposite shifts to meet ends meet...?
So no, I don't think the OP is unreasonable to be concerned by the level of disruption in her child's class and nor do I think it's a case of demonising children who don't behave; as a parent and citizen I just care equally about all the children who aren't able to receive the education they deserve, and about how that could further increase the social divide between those who can access private or tutored education to get the top grades and those who can't.