Obviously, you are not a happy person if you are an atheist and have to write about it on a cardboard box stuck in the back of your car. For the sake of anything you love, why don't you buy a Darwin fish or some type of catchy bumper sticker instead of putting some junk like that in the parking lot of a university? How embarrassing.
Do others concur?
Not stupid at all.
I think what we have going on here is easily answered by thinking about where this was seen -- a university parking lot. It's almost certainly a student. Probably one who just had an argument with a theist who said he couldn't be happy without God, and impulsively responded with whatever he/she had handy in the trunk of the car. It's life on a shoestring for most students, an endearing combination of idealism and poverty. I'm sure when he grows up and gets a job and 2.2 kids, he'll spring for the Darwin fish.