The damage is from what the media reports and how they spin it. So long as the media spins it to be a "horrifying" negative most people- who will never read a single one of the emails - will come away with the impression that the DNC did nasty dishonest things to stop Bernie Sanders.
And yes, the Democratic National Convention has done a lot of positive things, but people will still remember the negatives.
After all, look at the negatives that have been publicized about Hillary Clinton over the years - but when people look at her actual history she has done so many positives. I'm glad the Democratic Convention is promoting the positive records of our candidates. First off, it counters the negativity of the Trump convention. Second, it informs people who have only heard the negative spin.
Same for Tim Kaine. Yes, he gave one boring speech years ago but that has branded him as"boring" for most people. When he was governor of Virginia an anti-LGBT marriage amendment was passed - but it is all dumped on him by many sources despite the fact that he campaigned against it, didn't sign it and could not have stopped it. Here on DU people have posted the incorrect information multiple times, so many think that is Kaine's true record. And Kaine's true record of fighting for equality is amazing!