Whether riots are right or wrong interests me less than the fact that it would be foolish not to expect them if you disenfranchise a large segment of the population such that riots become their recourse. Those whose voices are excluded from the political process will find a way to be heard. That's to be expected. The solution is not to moralistically cluck at them for doing what you yourself would probably do if you were in their shoes, but to bring them into the political process.