What makes Ithaca, NY so evil to earn the bumper sticker?
How about, it's been voted the most liberal city in America, for years had an openly avowed Socialist Mayor, was known in its early days as "Sodom" because of the activities of the residents, and numerous other atrocities? :)
See the link to Behind Liberal Lines' profile page in my comment above, for much more history. It's fascinating!
Likely Cornell University plays into it as well.