Unfortunately I have to say it's not 100% true. The real independence movement was started from the right, look for "Artur Mas". The main slogan back then was "Spain steal from us". It's true though that Communists parties always wanted the independence, but the right parties have driven this process from the very beginning.

Lega Nord supports openly the independence of Catalunya because they are based on the same principles. Sure, there're differences, but the main idea is that they don't want to support poorer regions. Obviously they are not going to tell you that, but that's what originated the conflict.

In fact, some people in Catalunya (obviously a minority) were openly racist with other regions in Spain years ago (e.g., Extremadura, Andalucia), they even made ads in newspapers. Of course, this is not something that's really talked about.