It would take more than just living in a dictatorship, because before it would be moral to take up arms to resist the dictatorship there would have to be some possibility that taking up arms would actually accomplish something.
And in most cases, it just wouldn’t. OK, you shoot a few cops, blow up a government newspaper office, drive a truck bomb into a day care center.
And then what happens? Everyone rises up and the dictatorship falls apart? Or what is more likely, the cops die and the next month more cops graduate, they just open a new office, and they use the dead kids from the day care center as propaganda against the rebellion.
Yes, it’s morally OK to use violence to save your own life, at least in my ethical system. But overthrowing the government by violence isn’t exactly the same thing, is it? It has to be proportional, it has to have some chance of working. And it especially can’t be “we need to make things worse via random violence so that the current situation is intolerable and the sheeple finally wake up.”
Note that in the case of a foreign conquering army, making things tough on them until they get sick of it and leave is at least plausible. In the case of a domestic authoritarian government that’s not going to happen.
And of course as others have said, it’s not going to be bands of partisans wandering in the woods shooting it out with light infantry patrols. It’s going to be bombings, bombings, and more bombings. Sure, some soldiers are going to get shot in ambush, but it’s going to look a lot more like Northern Ireland. And of course if there’s an authoritarian tyranny the freedom-loving gun nuts are going to be supporting it rather than resisting it. It’s a classic feature of authoritarian movements to have paramilitary volunteers performing quasi-official violent actions in support of the regime. And it’s also a classic feature for the fall of the regime to be accomplished by disloyal regime insiders who see their chance.
Which of course means that the most likely outcome of a successful revolt against an authoritarian regime is the installment of another authoritarian regime, sometimes with brand new faces and sometimes with some of the same old faces. Restoration of representative government is much more likely to follow from the peaceful dissolution of the regime, on the lines of the end of the Franco dictatorship.