That's one possible harm, but I think it's also possible that people will take the allegations too seriously and withdraw from the political process entirely. One of the paradoxes of modern political life is that the elections that get the most attention aren't necessarily the ones with the greatest impact on our day-to-day lives. If you don't show up to the polls in November because {Clinton,Trump,Satan} will win anyways because of the rigged system, then you won't vote for mayor, school board, and local bond measures that can much more directly affect the policing policies in your town, the education your kids get, and the transportation infrastructure to get to your places of work or leisure.
However, I don't think this is a sufficient argument to motivate people who would refuse to vote because of the state of the presidential election. I think they would feel that local educational or policing policies are insignificant in comparison to the big-picture changes they now have no say in because their favored candidate was eliminated by corrupt party and media practices. They might still feel that they will be more affected by the year-to-year impact of foreign policy and trade policy than the day-to-day impact of a .1% chance increase of getting a bogus traffic ticket.