Where are your parents?

On Friday night our little family went out to Del Taco to eat. A headed straight for the playground with me right behind him. As we walked into the playground there were three kids, whom I guess to be between 9 to 11 years old standing on chairs trying to climb on the outside of the playground. The boy of the group had just managed to get a hold and was climbing up.

"Hey you shouldn't be up there."

The minute those words were out of my mouth the group of kids looked at me as if I had just said a bad word. They didn't get down so I reiterated the need for the kids to get down off the playground. They still didn't move, just looking at me like I was speaking a foreign language. I guess their mother finally noticed that something was wrong in the playground. She stuck her head in and said what's going on. "That lady told us to get down,"was their reply. "Well you guys shouldn't be up there now that there are little kids around," said mom. So the kids got down after they glared at me. Their mom didn't look to happy that someone else had ruined her kids fun. She was sitting outside the playground and kept glaring at me. Not too long after the kids had gotten down a younger sibling of theirs who was maybe 18 months old, tried to climb up on the chairs that his siblings had been on and ended up falling down and hurting himself.
I totally get it that mom's feel the need to get a break from their kids and let them play, maybe even play rough, but not inside a playground even when their are not little kids around. That's what bugged me the most. "Not when little kids are around." To me that phrase was just screaming you can do whatever you want just don't get caught! It upsets me to see parents who let their kids run rampant on indoor playgrounds. I see so many older kids trample down the younger ones or play on the outside of the playground, trying to get to the forbidden areas without mom or dad even trying to stop them. Why do they feel such a total need to be completely oblivious to what their kids are doing? I admit with one child I guess I feel extra protective of him, but I don't want to see his fun ruined either. I know most parents don't want to see their kids hurt, but what do you do when their kid is becoming a danger to yours? Am I overreacting? I was thinking maybe I could have handled it differently and tried to find the mom to ask her to stop her kids, but the reaction I got from the mom made me think that no matter what I said to her she was going to glare at me. So what do you do?