Q: Why do some Christians tell atheists that they aren’t going to heaven?
Do they think that bothers us? We don’t believe there’s a heaven and we don’t think Christians themselves are going to any place like that either. So why do they say this to us?
A: Short answer: They’re bad Christians.
Long(er) answer: You have to keep in mind that when someone says that, they really believe there is a Heaven. And for you not to go there (or more specifically, that they don’t want you to go there) it goes against all of their teachings about saving people and loving one another. They’ve already committed grievous hypocrisy, so throwing reason or logic into the mix isn’t going to help. It usually means they have nothing better to add to the conversation and have devolved into insults.
Just smile and respond to them like you would if a five year old told you that Santa isn’t going to bring you presents this year because you were bad.