They WERE slaves to their masters, but not slaves to themselves. What he really needs to accept is he saw himself through the eyes of his masters, but once he saw the people as people, and not product, then they were enslaved. Its all about the perception of the watcher.
I think its important to acknowledge we were seen as slaves to certain people, because it explains why we went through so much shyt, and STILL do. But, by also acknowledging that we are more then that, it allows us to reach more then the average BECAUSE we were seen as slaves. If you were once the lowest, there is nothing stopping you from being seen as great, you already know what being low means. This explains why we have had so many rich looking ways of dressing, but are the brokest in terms of real finances. Because we are at the bottom, we go over the top to not be seen as the bottom. This thinking created styles of dress that is being emulated all over the world!