This is a hot button issue for me, so here goes...
I have been taking my kids/daycare kids to these places since they started so many, many years ago. So I know EXACTLY what you are talking about. And yet, I see some rather harsh statements being thrown around here and would like to set a few things straight.
First of all, if you went to any of these playgrounds at any time you will see woman meeting in groups of 2 and 3 and they are talking to each other. This is what they do. They meet up in these places so that the kids can wear themselves out while they get a little personal time. It's bad enough that a busy mom has to go to a loud place like this to get some me time. They don't need to be judged for not "seeing" or "watching" everything.
Now, children have their ways before they get there. A child that budges in line will budge at home or at another park. So the parent going should know their child's propensities and should teach them well in advance that it's wrong. Most parents do try hard at this and most parents won't be upset if you point out to them what just happened. There's no reason to assume the parent will be mad.
That said, do you all realize that 60-70% of the play area is INSIDE of the tubes and you can't see or know for certain who did or said what?
I have taken 4-5 kids to these places, 1-3 times per week, for at least 15+ years and I read books, watch movies, and surf the internet and almost NEVER have any problem. I am able to hear when someone is yelling and always will get up and go see if it involves any of mine. It RARELY does. My kids are well-behaved and taught what is right before we get there.
My daughter is now 9 years old and just like her adult sisters that came before her, she LOVES these places. She is the kid that's up there making up games, getting kids involved, helping to push and pull tiny kids from one level to the next etc. She would never even think of hitting a child in one of those places. She has lost her cool with kids she is with every day and swatted someone and she has been dealt with at home. But she has NEVER done such a thing in public, not even once. So one day when she came to me just crying and crying, telling me that there was a child there that was being bossy, refusing to let her through the tunnels and that the child pushed her, I was about to leave with her. Then this uppidy woman came to me and told me it was all my child and that she was being mean. I'm really not THAT mom. I'm usually the first person to give the benefit to the doubt to both children and try and figure out what REALLY happened. I don't just assume that my daughter is in the right. But I KNOW my child in these places. I didn't say anything to the woman because she was clueless. Her child will be a bully for quite awhile and she might never get it until she's pushed into legal proceedings.
So to summarize my position....If you see it happen, go right ahead and tell the child in question it wasn't nice. Don't worry about the parent. If they are irked, so be it. Do give the parent the benefit of the doubt. It's POSSIBLE for any child to lose their mind in new situations. Don't JUDGE any parent that's looking at their phone or computer or reading a book. For PETE'S sake, they are just trying to get a few minutes to themselves. ALL moms should get this. If you don't, then you have a problem yourself of being just way too jugemental.