the DNC being primarily a club in which they get to choose the winner beforehand
Not at all. He did not get more votes in the primary and he did not get more superdelegate votes. If Bernie had received more votes than Hillary in either one it would be a different story, but he did not. So how can you claim that he was somehow cheated and the DNC always gets to pick the candidate?
The truth is that he lost because more Democrats wanted Hillary, face it.
