I am a bit conflicted on this.
A film about street gangs and postcode turf wars could be informative, and broadcast the futility and pointlessness of it all. I think that was the aim of the film (it was inspired by a YouTube series). I don’t know if this film’s message is successful or not. But it seems that the subject matter alone is enough to bring out these petty gangsters to the cinema where they are are encountering their enemies and the result is violence.
I am wary of banning a film or restricting its showing just because it is a subject matter I do not like.
Sadly, extra security and let the film play is about the best course.