Well, this is an excerpt from Aesculapius' guide "On the Feeding and Breeding of Governors and Generals":

Amazing though it may seem, riots and rebellion are good for your governors. These events force them to get tough and develop generally good traits such as ‘Authoritarian’, ‘Disciplinarian’, ‘Rabble-rousing’ and ‘Harsh Justice’. However, if such unrest is brought about by lazy tax policies – in other words if it happens when tax is anything other than ‘Low’ – the governor will certainly become known as a ‘Bad Administrator’.

So, just follow the above advice and keep the order at 70% and you should not have any problems. It's nice :)