You've been asked before why you single out atheists, so I won't ask that again. I would, however, ask you to consider the following.People are assholes to people that are different from themselves, be it by religion, skin colour or accents. The more different they are, the more likely they are to be demeaning in some way, and the more extremely they will behave. You and the alleged atheists were separated by differences of belief, which is commonly a huge part of one's life.
However, in this post you bring up something new. Your mother, the person which you arguably have the most things in common with, were incredibly mean to you because you didn't follow her exact doctrine.
Now ask yourself what is worse. People you have very little in common with following their unfortunate human nature and being disrespectful due to your faith. Or your own mother, whom you should be able to trust with everything, doing the same thing for the same reason.
Edit: Not only for religious reasons, but DESPITE her being religious.
When you're done thinking, you'll probably realize the futility and uselessness of this thread.