The letter opens by talking about how important YouTube has been for the campaign's efforts to get out copies of commercials, speeches, etc., but notes that the site's usefulness is being curtailed by "overreaching copyright claims."
But "despite the complete lack of merit" to the claims, the videos were pulled as per YouTube's policy.
The campaign can file a counternotice, of course, and YouTube will eventually put the videos back up (at this point, if a rightsholder still believes the takedown request was valid, he or she can sue the creator of the video). But this process doesn't move at either "Internet speed" or "campaign speed," and having crucial attack videos down for days at a time is apparently hurting the campaign.
The letter is yet more evidence of why human judgment--not just automated filtering or scanning--is crucial in such cases.
It's refreshing to see mainstream politicians (or at least their operatives and lawyers) speaking up for fair use and showing an understanding of the problems caused by overly-aggressive systems for flagging possible violations. Perhaps when those at the highest levels of government--not just the mothers of dancing toddlers--understand the problems here, a better copyright balance can be struck.