As an atheist, I don't go around bashing on others' beliefs - as long as they're respectful to others and don't use their beliefs to police others.
A grandma on her deathbed, trying to find comfort in her faith? Hell, I will sit with her and confirm that she's indeed about to see her dead husband and spend eternity with him. Because at that point, being kind is more important than being right or debating theology.
But, the moment you try to use your beliefs to dictate how others live (beyond basic morality, going beyond the golden rule), out comes the "fuck off with your imaginary sky daddy" argument. You are free to live your life by any doctrine you want, as long as it doesn't affect others negatively. You don't want to eat meat? Sure, go for it. You don't want to eat pork/beef/seafood? It's your body, your choice. You don't want to get an abortion or transition to a different gender or be in a gay relationship? Again, it's up to you. But the very second you try to tell others to live by your rules, you can fuck right off, and then fuck off some more just for good measure.
And it's not like I'm not open to debate. I guess at the end I'm more agnostic rather than atheist, in this aspect. I welcome theological debate. I'll gladly argue about it for hours as long as you're respectful. I've got a bunch of theist friends - Christians, Muslims, Hindu, a variety of pagan/wiccan witches, and so on - with whom we do sit down on occasion with a drink or a joint and debate various aspects of belief, religion (organised or personal), their effects and influences on society and vice versa. It can be a brilliant topic of discussion as long as everyone respects the others and listens to their side. After all, every single person has their own point of view formed by their upbringing, their life experiences, and so on, and these are equally important regardless if you agree with them or not. But it's equally important to understand that these debates aren't meant to convert anyone. They are there to convey a part of you you find important, so others can better understand you. Understanding why one turned away from, or turned to religion, and how that helped them as a person.
To summarise: religion is like a penis. It's okay to have one, it's okay to not have one. It's even okay to be proud of (not) having one. Hell, it's even okay to think yours is better than others'. What's not okay is pulling it out in public and trying to force it down others' throats, or try to legislate in the form of a dick measuring contest.