Why couldn't I post this to Youtube?

I was trying to post this today as an example of a particularly bad television ad, an ad by Paul Nelson attacking Rep. Ron Kind for apparently voting for the budget and pointing to scientific studies undertaken by the NIH. I was going to post it in contrast to this ad by the Yes on 89 folks in California, and talk about how some ads just keep up from voting at all.

Find the ad also on Nelson's website here.

But, now I'm wondering why Youtube wouldn't let me post the Nelson ad in the first place. I tried twice this afternoon, and both times it was rejected for "terms of use violations." Political ads aren't copyrighted, they are part of the public domain. Also, Nelson needs to be mocked. So, why reject the video?