[Stone Mountain]

What would an atheist bumper sticker be?

How about, "I don't believe in God" or "God is a Myth" for example?

The answer is, an atheist monument is absence of a monument. An atheist bumper sticker is absence of a bumper sticker. Since that is not satisfying to some atheists, instead of proclaiming their atheism they need to vandalize my monuments or insult my religion.

Wow, that's some straw man you managed to erect and bring down...

[annalex]

Yes, those would do as bumper stickers. Although I still don't see why anyone would gunk up his bumper with statements of what isn't. I wouldn't be tempted to have a bumper sticker that says, for example, "I don't have a goldfish".

So what would an atheist monument look like?

Regarding strawmen, -- surely you have seen blasphemous bumper stickers or heard of Christian monuments removed by court decree. They were not made of straw.