With respect I completely disagree with this - the reforms to working conditions and the state of our societies in Europe which have happened since Engels wrote 'The conditions of the working classes in England' or Marx 'Capital' have improved because of gradual progress in western democracies introduced because of peaceful protest and people working within the democratic process, on things like mandatory schooling, no child labour, minimum wages, right to assembly, health services, benefits etc. That's a far longer time-frame and was not influenced by the USSR, either in funding western political groups or acting as a sort of bogieman for western governments.
I disagree that revolutions and the attendant violence and destruction are necessary or useful in deposing tyranny, quite often they produce the opposite effect, as the two examples you initially brought up show.
The only country where you can try and talk of a continuous peaceful development is post-Cromwell Britain, which is why this country is still, in many ways, the less socialist of the lot (and getting less so by the day, I could add). Still, the influence of Soviet ideals was so strong even in this land, that there was stuff like the Cambridge Five, something that today is completely unconceivable.
Violent revolutions are not always necessary, but they can (and did) provide inspiration for wider movements.
I know my history well enough, I'm not denying that revolts often (but not always) result in weak political structures which are prone to collapse in the short term; you only need to look at the current wave of Middle-Eastern "springs" for confirmation - from Tunisia to Egypt, in practical terms they're now worse-off than under their dictators. Still, they play a often necessary role in putting the fear of consequences in the heart of established elites who would otherwise refuse to change; places like Saudi Arabia are now grudgingly considering improving conditions of their women, for example.