Did the parents who sat by and didnt seem concerned about hitting (for example) or mean behavior say why? I'm assuming this was discussed amongst the group...what was their rational?
I was at one mom's house (who I really like, I think she's a wonderful person) and her dd, who was about 7 or 8, walked in looking for cream cheese or something for her sandwich. The mom informed her they were out, and the dd proceeded to scream and berate her mom about this. The mom didn't say anything, the dd calmed down, and they went about making a sandwich. Now, maybe after I left she addressed the behavior with her dd, but honestly, it felt to me like this was just a ok stuff that went on all the time. No way no how would I continue to help my child make a sandwich after they screamed at me. But hey, if that works for her, fine. It just doesn't work for me.
But I know what you mean about differing views of acceptable behavior. We tend to hover somewhere in the middle. We allow our kids all sorts of freedoms that many other parents find pretty shocking. But then I tend to feel that way among the radical unschooling groups, and most of it is directed to how the kids treat other people. Wild stuff like the chairs you mentioned, or jumping off the equipment or what have you - that generally doesn't bother me. I only care if someone is going to get hurt.