How to respond to "God bless you" statements

[Fromper]

Cause wishes don't cost me anything.

You may have stumbled onto a bumper sticker: "Religious 'cause wishes don't cost me anything." I like it!

But then the bumper sticker would cost something, so it would no longer be true.

For me it depends on the context. If they're some nutter preaching at me in the street they'll be ignored or get a "Fuck you!" from me. If it's just a kind old lady's way of saying thank you, I'll take it as such and just say "Thank you" in return.
The difference being, one is being kind, and the other is being a dick.

Again, my point is the PR from letting people know that atheists exist, and we can be good people. What if that kind old lady is a nice person who just assumes all nice people must be Christian like her? Introducing her to some nice people who aren't Christian would be an education to her, and could help in the long run with ending religious discrimination.

To put it in context, I keep saying this is like the PR job the LGBT crowd has done. Thirty or forty years ago, if a nice old lady told a gay guy "You should meet a nice girl and settle down", he probably would have just smiled and nodded to avoid a confrontation. In the last decade or two, the gay guy would be much more likely to let the old lady know that he's gay, so he's not looking for a wife. And if the old lady thinks he's a nice guy before finding that out, then suddenly, gay people aren't so bad in her eyes. It's because so many Americans know someone who's gay that LGBT rights have made such advances in recent years. We should be copying that approach when it comes to atheism.