This is really more of an essay on communication, but let me start with god.
I'm atheist. In the literal sense of the word; a-theist, without theism, without a belief in a god. I came to my atheism through a great deal of thought, careful exploration of religious ideas and searching my soul for what felt right to me. It wasn't a light decision, nor an obvious one given the religious culture of my home town. I had to think about it. Which is why I talk to religious people the way I do.
You see, I assume that someone who has a strong religious belief also came to that after a lot of thought, exploration, and honest attention to their own heart. When someone talks to me as if my atheism is just some idea I picked up off the street, when they tell me all I need to do is ask myself the deep questions, or look at a baby, or read the bible in order to see that god is real, I find that deeply disrespectful, dismissive and offensive. No matter how good the intentions and how deeply that person cares about my immortal soul, that kind of statement starts with the assumption that I haven't actually thought this through.
I'm not a big fan of assumptions in general, but they are built in to the human mind, we couldn't function without being able to assume things we can't substantiate. We speak from assumption all the time, we can't help it. However, not all assumptions are created equal. Some will surely make an ass of you, but it's possible to instead assume in a way that almost always leads to the best possible outcome.
In the same way that a devoutly religious person could speak to me with the assumption that I'm just a little misguided and only need the right bible verse to turn me around, I could speak to a religious person with the assumption that they only hold that belief because they grew up in it, that they've never examined it, and if they did, the scales would fall from their eyes in no time.
If I do make those assumptions, everything I say to them is going to be colored by that, even if it's just meaningless smalltalk. Without even being conscious of it, I'm already condescending, already looking down my nose. And what if it's not smalltalk? I could decide to educate them, filling them in on all the logical inconsistencies of the bible and pointing out how there is no way Noah got two of every species on that boat. Furthermore, everything they say is going to filter through my screen of assumption. They may as well be speaking through a kazoo, I'm not going to take anything they say seriously, if I even hear it to begin with.
My assumptions could be wrong. Maybe they don't take the bible literally. Maybe religion is a complex philosophical world view for them, rather than a pile of dogma. Maybe they converted after a life of atheism and years of study and consideration. Maybe they have a doctorate in theology and can think circles around my limited understanding of faith itself.
I could just be wrong and acting like an ass. Or, I could be completely right and acting like an ass. The problem is not the accuracy of my assumption.
What happens if I assume that they came to their faith by a path just as long and rigorous as my path away from it? The worst case scenario is that they are in fact a silly person with a frivolous faith, and now they think I am a pretty good person because I spoke respectfully to them and actually listened to what they said.
The best case scenario? I learn something.