Postcolonialism is the invention of some rich guys from India who saw that they could make a good career in top Western universities by playing on the guilt of white liberals.
Fascism is relatively easy to explain. It is a reactionary phenomenon. Nazism was some bad guys having some bad ideas and unfortunately succeeding in realizing them.
A typical guy who buys organic food doesn't really buy it in order to be healthy; he buys it to regain a kind of solidarity as the one who really cares about nature. He buys a certain ideological stance.