That is a little Naive! Why do people buy Apple products, they are no cheaper, they aren't really any better but they are cooler. Apple knows that great tech isn't enough, they know a strong sense of focus on solving consumer problems isn't enough.
They know that their brand is everything! Their brand is on their products, billboards, tv screens, movie screens, their brand is Tim Cook, their brand is their store presence. Their brand is everything they choose to associate themselves with, and they associate themselves with which are only ever liberal, free minded, socially positive ideals. MLK is the most positive icon of 20th Century American history. They identify strongly with MLK's brand and thats great marketing.