I HATE WHEN PEOPLE DO THIS! (remedial work or extra exercises for the child to do in order to gain strength and awareness is another story). If an entire group isn't behaving or the child isn't showing any interest at all, I offer conditioning/exercises or just sit down, but I try to make it a choice and be very even with it.
There's a lot of people working with kids who are more comfortable with adults (and no I don't think this has a lot to do with being a parent, I'm certainly not and won't have school age children for awhile), and I get that, but you need to learn some coping skills. Some coaches are getting way overinvested and take a child not making corrections personally. it's ridiculous. I can always tell the coaches who are "above" rec classes but also don't want to learn about kids or realize how LITTLE some of these kids are or how high the expectations are. Yeah, it's team gymnastics, expectations should be high, but we need to have some sense of scale here. People just boggle my mind sometimes. I can't post in the parent forum but I read that thread with the limbers in preteam and it horrified me enough I felt sick.
I try very hard NOT to single anyone out. And to find something positive the child is doing as often as possible. If the child is not strong, weaker than the rest of the group - so what? Watch that child during conditioning, push them a little to "fight" with encouragement, and tell them how proud you are of each gain in strength they make and what your next goal for them is. I mainly coach girls, although I sometimes work with boys, and I know things can get a little different with them - they tend to not take things nearly as personally and often take a lot "more" in order to listen as a group. But I'm just going to talk about girls here.
Finally, coaches and instructors need to recognize the difference between behavior and safety issues and not being able to do gymnastics. There are consequences for behavior and safety issues, but you can't punish a child for not being able to do something in gymnastics. It's silly. Attitude issues may be a gray area, and this is where some discretion has to be exercised based on individual personality, but in general my feelings towards attitude issues are that you can never control a child and how they're going to approach this sport, you can only put an environment in place that will hopefully encourage them to make their best of their time in the gym. If despite best efforts they clearly don't want to be there, then there are natural consequences: progress will stall, you won't get to move on to the next skill/drill that other can work on, and so on. We should be trying to teach kids life skills here and part of that is accepting a system of natural consequences and accepting that we may see a child struggle before they succeed, whether due to attitude or developmental ability.