The people who are dumb enough to have a life long grudge because one candidate they liked didn’t get the nomination were never going to support the party to begin with.
The poster is claiming that the DNC rigged the election against Sanders, or at least were so unfair that it’s fair to say he might have won otherwise. If people believe they are actually this corrupt, it will turn people off from the party. I’ve already stated that this is not about the dopes who have convinced themselves, with no evidence, that he actually got screwed. This is about stopping other people from falling for the lie.