As an old man who grew up in Swansea, I am also disgusted with the behavior of the teenagers AND the jeering adults.
First of all, seven police officers were hurt at the scene by bottles and bricks thrown.
Secondly, this was not a new problem for the council areas of Swansea, as many residents have constantly complained for months (and years) about anti-social behavior.
The areas of Blaenymaes, Townhill, Mayhill, Penlan, etc. always had a reputation of tribal gang culture, even when I was a young lad living in the Swansea Valleys during the 80's. They were always known as Police 'No-Go' areas as the youngsters were notorious for vandalism and joyriding (often setting alight the cars on Kilvey Hill). We used to joke that Bonymaen was twinned with Beruit!
Since I have left South Wales (30 years ago), South Wales has become prosperous with massive amounts of European & UK funding spent in local regional developments, to improve housing, jobs and amenities in the Twin Cities (Swansea & Cardiff). Enough for money was spent, that the Welsh Assembly (now Sennedd) could have built a dual carriage from Camarthen to Caernarfon and still be pathed in gold! But that's another story.
So, irrespective of lack of police presence or social culture lack of jobs blaming etc. the problems have always layed with the rioters, their guardians and the senior managers who manage the police. The areas should never be feared by the local residents, the anti-social behavior should never have been overlooked or given lesser sentences by the courts, the teenagers and younger kids should never have been allowed to congregate at late night, AND the adults should have known better to not allow such disgraceful behavior happen. But when the adults were able to do similar things when they were younger and got away with it, and their parents before them, do we expect the youngest generations to learn what is respect and decency?