The first bumpber sticker that I remember from my childhood was circa 1979-1980. The sticker read "America: Love it or Leave it!" I also remember some stickers that had suggestive remarks regarding what Khomeni could do with himself.
I recall Mickey Mouse with a "Hey, Iran!" and a one-finger wave.
My nominee for most ubiquitous AND asinine sticker, however, was always the one that said "Question Authority." Whenever I see someone with that sticker, I always make it a point to tell them, loudly, "NO!"
They almost never get it.