I sympathise with you. It is absolutely appalling how these gangs of louts have been allowed to take over areas without any consequences, making life horrible for everyone else.
I've wryly laughed at posters who have implied it is somehow your fault for going into the park when you saw them there.
That is the problem in a nutshell-it's your fault because you put yourself in their way. What a piss poor attitude-we should all back away and let the fuckers take over the neighbourhood.
Sadly, though when some parents, schools and the police fail to enforce punishment and consequences (dirty words to some). Totally laughable that some posters think they are anti social threatening fuckers because not enough money is spent on ping pong tables.
They were in a park, for fucks sake-that's a resource right there- and do they use it for games-no they use it to intimidate. The barbarians are through the gate and there is nothing that can be done and their dominion-and in many areas it is dominion-is aided and abetted by those who think to say boo to them is a mortal sin.
That includes the police who, if they do attend an incident such as the one you've described-will simply have a chat to them, instead of putting a few of them in the back of a police van and from there, into the youth court.
Maybe it will change in 50 years, when the pendulum finally swings back.
You've had an awful experience-many parks are no go areas because of these shits and you are right to be still fuming.