Who says they have to reveal the information publicly? Jack is surrounded by enemies and information has a way of spreading even without the advent of technology. And even if some people did go public, congrats now they're martyrs to the cause of 'Usurp King Jack'. It only takes a few sparks to set a fire and at the moment it seems like Slibah is sitting on tinder and leaves. 

As far as revolutions go, the basis of Jack being no better than a tyrant. Forcing people to work with questionable and harsh conditions, suggestions of literally killing people for being like "Man, FUCK Jack" and any number of atrocities that are sure to come up. Someone being publicly executed for speaking up might have some cheering, but it could also have some using that as further fuel. Hence the martyrdom clause. If people are forced to shovel shit, don't be surprised when they start flinging it back. 

And if he doesn't want to kill, maybe he should show some restraint going forward.