Your scenario is similar to the New Robocop(Underrated thought provoking movie, IHO).

Your scenario and most of the comments make the following assumptions and are missing the point of the Singularity phenomenon, many of them are based on historical precedent:

1. The dictator is Human.
2. An assassination on a single Human or group will change anything.
3. Some sort of fifth column/beneficial insider could exist.
4. Rebel technologist could create something the old decadent class is not prepared for.
5. There is an underclass of poor and subjugated people.

I'm assuming Strong AI exists for your scenario. This would be needed for semi-autonomous Cops who can make judgments and apply violence (Force) where and when needed in novel arising situations.

All Assassination attempts Rely on exposure and information. In a world of strong AI like you suggest

It won't be human engineers or hackers who might be able to provide an underground or a distribute a pack. Strong General Artificial intelligence, the kind that a Dictator or Dictator class would need in your scenario for autonomous thinking cops, would and will likely be improving their own code. The next Global Dictator will be a Super Intelligence.