I'm working in a small office of about ten employees, all of whom are religious apart from myself.
Although I'm open about my atheism and write about it on my blog, I am careful not to discuss religion at work. That is, I will not bring up the subject. However, if anyone else mentions it, I make a point of saying something. Since I was brought up Christian and read their book as well as went to church for many years, I am quite comfortable discussing any aspect of it and probably know as much about it as my colleagues, just minus the belief.
Recently, a colleague asked that I do not make any comments because his beliefs are strongly held and he took offense to something I said, without revealing what it was. I thought the comment was odd, since the last time I mentioned religion was several weeks ago. At an office meetup in a restaurant, someone else raised the subject of bacon being against some religions. Thus I pointed out that wearing mixed fabrics and eating shellfish are also forbidden, and commented that the rules of this deity seem somewhat arbitrary.
I thought this was unfair, given the habit of my superior, who often tells people, if I sneeze, "Don't say 'bless you'. It offends him." It doesn't offend me, but his comment does. It's not as if anyone is literally intending some sort of religious blessing whenever anyone sneezes, so the end result is that my atheism is occasionally brought up as a topic of discussion, whether I want it or not.
The person who suggests that he doesn't like my comments is very young and insecure. How do I politely tell him that I do not intend to make any comments about religion, but also make it clear that if the subject is raised, I can talk about it just like anyone else? And he probably won't like what I have to say...
Commenter Erik asked about my location... I'm in Johannesburg, South Africa. Although there's a strong online atheist community, most people are religious here, and being an atheist is pretty rare. It's normal to be the only atheist in the office.