I think the difficulty with this as a general proposition is that not all rebellions/coups/revolutions end up like Syria. With the benefit of hindsight it seems

I think the difficulty with this as a general proposition is that not all rebellions/coups/revolutions end up like Syria. With the benefit of hindsight it seems clear that almost everyone would have been better off leaving Assad be. But this can't be universally true for two reasons. First, not all revolutions end up like Syria. Relatively bloodless coups are common, and even many civil wars with fighting are much less bloody and disruptive than the Syrian civil war - the US war of independence might be one example. The second is simply that if no revolution is justifiable, there's nothing to make a despotic monarch give any attention to the needs of their people - as the people will 'sensibly' not revolt anyway. So on the one hand Germans shouldn't resist the holocaust, or Cambodians the killing fields, and on the other you get figures like Charles I and various French Louis' making tensions in their countries far worse because they believe their position is secure. Neither is a template for a happy society.