This doesn't surprise me when you see the kind of things some parents PUSH their children to do ~ very young children put under all the stress of being beauty queens, children pushed to stardom at a young age, etc. (I am talking about the EXTREME cases here ~ not parents who encourage their child's talents); it's all a form of child abuse as far as I am concerned.
In the UK we have laws about the age children can be in pubs, the age they can watch certain videos etc. These children were put in this situation by their parents, in the midst of an ADULT evening ~ drinking, adult cage fighting going on .... the parents of these children knew exactly where their children were. They put the children in a situation where they were on show, trapped in a cage like a couple of fighting cocks; it was an adult evening and the children should not even have been present, let alone taking part. Goodness knows the damage this kind of thing does .... it is WRONG.
The social services/police should be dealing with this but I doubt from what I have read so far that anything will be done!