"He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God." John 3:18
Christians love to put John 3:16 on signs, and tracts, and websites and whatnot, and they can't understand why anyone would not accept the "Good News" of Jesus H. Christ. The quote above, however, isn't used nearly as much in Christian propaganda. It's the logical "other side of the coin," isn't it? That "God so loved the world" stuff might sound pretty nice to someone who's in the Christian club, but John 3:16 doesn't really mean all the world, does it? Oh no, those who don't believe are toast, as it clearly states a couple verses later.
And here's another problem, as I see it: what about those who used to believe, who really thought they believed, and don't any more? Which group do they fall into? I mean, I "accepted Jesus as my Lord and Savior" (several times), but I don't believe any more. I'm assuming, by the Christian definition, I am not "saved" any more. Now many Christians will presumably have a problem with me, because their belief system isn't really set up to deal with someone who received the gift of salvation, only to decide later that the gift didn't exist in the first place. That's why you'll often hear Christians say that apostates (like myself) "never really believed in the first place." They just thought they did, but they weren't really filled with the Holy Spirit. They were acknowledging Jesus with their lips, not their lives, etc., etc. Whatevs.
Funny thing is, in this "progressive" America in which we live today, you're rarely going to hear a Christian tell you right to your face that you're "condemned." I guess, if you push them hard enough, lots of Christians will admit that you probably are going to hell if you don't believe. But lots of the more open-minded ones will say something like, "That's between you and God," and promise to pray for you. The thing is, even those open-minded Christians are still assuming that the atheist is in a pretty precarious position. The "between you and God" response often means the person is hoping God will just bend the rules for nice people, which kind of negates the whole "accepting salvation" thing, in a way.
Anyway, we know the truth, don't we? It doesn't really matter if we're condemned or not, because the whole eternal punishment/eternal reward thing is a crock. "Life's a bitch, then you die..." I'm okay with that.
It should be enough for a Christian that an atheist can demonstrate that they are a good person. If that atheist approves of Jesus, so much the better as far as the Christian is concerned.