Once again, I'm a racist

The attacks grow ever more strident as Barack Obama supporters decry anyone who would dare vote against their candidate as being a racist: http://www.vindy.com/news/2008/sep/16/democrats-accuse-locals-of-being-racist-toward/. I'd love to say that this is an isolated incident, but the truth of the matter is that the very converse is true. I'm frankly sick of being told that there can be no reason to oppose Barack Obama's candidacy other than racism. It's wrong, and only people who can't argue intellectually with their adversaries would make this argument. So, why do Democrats keep doing it?