Errr Stalin was responsible for the deaths and/or suffering of an estimated 20 million people +, many of them his own. Sounds like perfect harmony to me.....you nut!
Part of the point of Stalin's quote is that once you can justify killing more than one person, it is not hard to justify killing many more. Lives just become meaningless numbers on a balance sheet, so you start with rebel clensing and end up with mass murder, not peace.
You might want to pick up a history book or two...harmony and 'world peace' are slightly different things though arent they? I assumed we were talking about conflict from one country to another.
If communism took hold allover the world it would be pretty damn hard to get out of, thats why the west fears it so much, basically because its a bit of a one way street, once you're in, you're in so there would be more of a world identity than individual countrys to fight each other.