Bystanders don't want to live in a society that uses tanks and poison gas on retired veterans or that kills protesting students; leaders who try to use those tactics tend to get voted out of power -- or else overthrown.

Just because governments often employ violence just before they loose power does not mean that employing violence was the cause of their downfall. Many sick people take medication just before they die. Sure violence may do them no good, like an aspirin does no good for a brain tumour, but it is hard to therefore argue that aspirin is the cause of death. The assertion is particularly dubious since historically speaking governments have used a whole lot of violence and this actually seems to have often saved them. Even in modern times we have plenty examples of this.

This Robin Hanson post seems somewhat relevant:

Once upon a time, poor masses suffered under rich elites. Then one day the poor realized they could revolt, and since then, the rich help the poor, fearing the poor will revolt if they ever feel they suffer too much.

Revolution experts mostly reject this myth; famous revolutions happened after things had gotten better, not worse, for the poor.