I quit my last job, even though I really needed it. It was nice of them to give me the job to begin with, but on my application I said I couldn't work earlier than 1pm on Sundays, so I could always make church. I thought I was being pretty cool to them because a lot of Christians around here won't work at all on Sundays. I was wrong. One manager was angry about it, and talked about it to the employees. Apparently Sunday morning is a busy time. Soon it became a public joke to everyone. And for some reason, people become SO EXCITED to let it be known they don't believe in God, once they find out you do. It became typical discussion for religion to be mocked. That on top of the fact that it was a really crappy job, and I just couldn't take it anymore. Perhaps I should have stayed and tried to let them know or understand me somehow, but mostly I felt pushed in the corner. I know this isn't the most major persecution that has ever happened to anyone, but it stunk.
Most folks get resentful anytime some special accomodation is made for another. (I'm a nurse, I've worked more Sundays than I have had off, BTW)
As far as the folks getting excited to let it be known that they don't believe in God, I figure that is human nature. Before I came to Christ I was an atheist. Let me assure you that many Christians can be and are as nasty as the atheists you describe to someone who does not share their faith. A lot of people are just plain catty.
Overall, it sounds to me like resentment not because you are a Christian but because you received special accomodation because of it. You don't know how irked I get when someone suggests that all of the childless people here should have to work Christmas in deference to those who have kids. (Hey, I might not have kids but I like Christmas too!) Most people don't want to see someone else get out of an onerous task (like working the heaviest shift) for whatever reason. If you were absent from a particularly nasty shift because you were taking a class, you would likely get a similar reaction.
Since you've left that job already, there is no point stewing over it. It's history. What you can do is learn from it.
Many many businesses are not open at all on Sundays. Those might be a good employment option. Another option might be to work a 7 day business but ask if you can work every Fri and Sat. (prime party evenings) or any other generally disliked shift job
in exchange for Sunday mornings off. Doing this is unlikely to stir resentment among your co-workers. It might even promote gratitude. I have degenerative joint disease, so I'm a little slower than most younger nurses. This could easily cause resentment if they felt they were being forced to carry my load. How I deal with it is to work the hated night shift, which they perceive as sparing them from having to take a turn on that, and I also volunteer to do the lion's share of the hated paperwork, which is appreciated by all.
There are ways to get an accomodation which do not promote resentment, but they require that you give something more or sacrifice something else in another area. Where I work we would all kiss the feet of any person who worked every Friday and Saturday evening or night (party time!) in exchange for Sunday morning off. If you go into your next job and voice a willingness to take on something undesireable
in exchange for getting your Sunday mornings off you may see a totally different reaction from your co-workers.