I can't prove it, but I suspect some contributors are stuffing the ballot box on the SLOGANS page- but they're doing it for themselves, not for the slogan-in-question.
What makes me think so is the rapidity of "stupid" votes that appear within seconds of putting it up.
I'm just saying that for some people, any competition has to be squelched in any way, at any time... by loading up the negative votes, theirs have a better chance.
But then again, I'm from Chicago, home of The Stuffed Pizza and Ballot Boxes...