I can see all points of view here.
Yes kids will be kids and play, however letting unruly children run wild when surrounding people are trying to enjoy peace and quiet is uncalled for.
Kids learn from their parental teachers and if they are allowed to run riot and ruin peoples fun then yes the parents are to blame for not reigning them in.
Not everybody wants to listen to kids screaming and shouting regardless if you are a parent or not, if you cant control your children in a public area to a certain degree then you are not being a parent.

You're born, you take s**t. You get out in the world, you take more s**t. You climb a little higher, you take less s**t. Till one day you're up in the rarefied atmosphere and you've forgotten what s**t even looks like. Welcome to the layer cake son.