The flag is just a symbol of different things to different people. The swastika had a long history as a symbol before the Nazis got a hold of it. Buddhism uses the symbol, as well as Hindus. Although, they have reversed the symbol to the left to try and distance the association. So it can represent many things to many people. But that symbol in particular, got a serious bad rap after the 1940s.
http://en.wikipedia.org/wiki/Swastika
I think the same thing can be said about the confederate flag.To some, it ties them to their ancestors who might have been great warriors back in the day. However, if you are of African or minority decent, it is seen as a flag of repression. It represents kind of a last stand of seeing certain groups of people as a slave class. So, you can see why these simple symbols can stir up a great deal of emotions.
http://en.wikipedia.org/wiki/Confederate_flag
I think when you get deeper into the roots behind the Flag, you find more history that can clarify the meaning. It is a ashame that some symbols like the swastika, will always be seen differently by the Western cultures. A symbol of everything we hate as Americans. At the same time, it could be the best symbol someone lays eyes on in a totally different situation and culture.
As far as social movements go, they tend to bond people through a common interest, or proximity. Urbanization and industrialization are credited with jump starting movements early on. Whether it was a union or a social gripe, these factors along with advances in communication made it possible to have social change.