It's pessimisitic indeed, but perhaps NOT that implausible, given that the regimes in question, particularly the Nazi example, were prediposed to removing the threats to stability by the simple expedient of having them killed without fuss or bother. They had proven to be effective in countries where they were dominant (How effective the French Resistance would have continued to be in a country where the Germans' weren't using it as a staging post to invade Britain, but were in control is an interesting one to ponder)
Read Robert Harris' "Fatherland" for a depressingly plausible look at a world where the Nazi's won.
Similarly the move to free slaves would have been not only derailed, but could have been effectively discredited as a political philosphy by a Civil War where the South won (Out of genuine curisity, after the Civil War, how many pro Slavery politicians were in positions of power?), and they were the ones establishing the new order of things. There may have been references to a resistence movement in this story, but I can't recall offhand.