I don't understand bumper stickers. Who cares where I've been, who my alma mater is, what I ♥ or whom I voted for. Some are funny, but it's the automotive equivalent of wearing the same funny T-shirt day after day. The joke gets old.
I really don't understand the political and controversial ones. Who changes their mind on an issue because of a bumper sticker? Who thinks, Hmmm, that's a swell slogan. I guess I was wrong all along? If anything, someone who disagrees with my sticker will think I'm a fool, a jerk, perhaps a fascist. If he happens upon my message in a parking lot he may feel morally obligated to slash my tires.
Then again, a bad joke or a tacky banner from a radio station might elicit damage too.
This chart sums up how bumper stickers appear to their target audience.
You have been warned.