If you want a bumper sticker that will offend everyone, try:

Nuke the gay whales for Jesus!

Or, you could do what my son did -- have a bunch of pictures of a wood screw printed on
self-adhesive round stickers about 2" or so in diameter (5cm).  Then, in parking lots etc.,
stick them over the little hearts on other people's bumper stickers.

Gives a whole new meaning to:

I (heart) New York, or
I (heart) my French Poodle.

Bill in Arizona