Depending on where you live and how open you are with others about your atheism, you may have had an experience like what I'll describe below. For those who haven't, I'm guessing it will not be too difficult to picture it and consider how it might feel to have it happen to you.
Imagine that you have been getting to know a new friend or potential romantic partner. You are in the very early stages of what could be a great relationship, and the two of you are still getting to know each other. You don't yet know whether you are going to hit it off. What you do know is that you are not interested in having a relationship with someone based on false pretenses. It is important that they know who you are and accept you on this basis.
And so, you decide to do something risky and put yourself out there. When it comes up naturally in conversation, you say something like, "Actually, I don't believe in gods. I'm an atheist." The other person gives you an odd look and replies with something like, "Yeah, okay. Why wouldn't you be?" He or she continues on with the conversation as if it was no big deal. There's no look of horror, no backing away from you, no threats of hell. It is almost as if your big disclosure was no more Earth-shattering than it would have been if you had said that you liked pizza.
I have only had this experience a few times in my life, and the feelings of joy it has provoked were indescribable. All sorts of other things can cause these new relationships to crash and burn, but it won't be my atheism this time. This experience has been so unusual that I cannot help celebrating the few instances when it has happened.
It is sad how rare this experience has been. The norm looks very different. It tends to involve an expression of horror, sometimes accompanied by an audible gasp. It is the sort of reaction I'd expect if I told someone I was a sex-offending Nazi. This expression is often followed by some combination of awkward pauses, stammering, physically backing away from me, Christian proselytizing, or threats of hell. And of course, the resolution is a hasty end to the potential relationship. Most of the time, the person abruptly ends all contact. There is rarely any sort of explanation; it is as if I suddenly no longer exist.
To be honest, I think I'd prefer this outcome to an alternative I have experienced in the workplace more than a few times. This scenario goes exactly like what I've just described except that the person does not end all contact. That isn't possible when we work together. Instead, they minimize contact with me, and it seems like the relationship has been drained of anything that feels human. They treat me coldly, making it clear that they are only interacting with me because they have to. And in some cases, I have heard them disparaging me behind my back. "You shouldn't trust him. He's an atheist."
When I think of normalizing atheism, working to help others understand that anti-atheist bigotry is bigotry, or trying to end discrimination against atheists, I recognize that many atheists are dealing with things far more unpleasant than anything I have described here. There is a litany of indignities inflicted on atheists that make everything I've said here seem trivial. Still, I can't help thinking that many of them start with that flash of horror one sees on the face of some people right after they learn that we are atheists. This is an experience I'd like to be far less common than it is. We should all have the experience of meeting more people who don't care that we are atheists.