Not quite sure a riot is ever a 'good' response to anything. I mean, do you go with something like the French revolution?
Certainly in this circumstance a riot is going to achieve the sum product of f*ck all. American policing is broken for a multitude of reasons, as has been discussed in this very thread. Training being the largest, but also recruitment, standards and so forth.
The five f*ctards that did this have been fired, and are being charged through the legal system. There was no cover up, there is no systemic protection, there is only a horrific act done by horrific people and hopefully personal consequences for them.
For me a riot in this case would just be an excuse for those with ulterior motives and causes to get media attention. And if there is a riot, people will likely get hurt, and likely die.