Whenever someone in the church offends my mom, says or does something she views as wrong in anyway, she will exclaim, "and they are in the church!!" Like because they are in the church they should know better and do no wrong. I just want to go off whenever she says that, but just bite my tongue...or when she will have nothing to do with someone until she finds out they are mormon, then they all of a sudden are the greatest thing since sliced bread!!

During a family reunion in Utah my mom was having some breathing problems due to the altitude. I took her to the ER in American Fork. WHen the Doctor came in and introduced himself she said, "Dr. Young. Well, that sounds like a good mormon name." As if should wouldn't have gotten just as good of care from Dr. Reubenstien.
I just wanted to crawl under the chair.

If I was in there (just speaking for myself), I would've snapped, "Yes, and what about it?!"

observing & acknowledging sin in fellow members is a sin in its own right! and sin is to be strictly avoided by good latter day saints. its not a sin that my good member Mom is going to be doing. Besides if Members complain about other members then some non member might hear of it, and that would go against the stellar image of the Church! Even pershaps preventing some one from being converted! ( GASP!) perish that thought !

Whats wrong with your Mom? She really needs to step up her good member game!

I have non-Mormon Christian friends and members of ext. family.

The standard question when I say I've met a new friend or so is "Oh, is she/he Christian?"

When joining an association/club of some kind the question is rephrased:

"Are there any Christians there, though?"

"Do they drink?"

...

I don't think it's just a Mormon thing.

People make associations and connect to people that they think are most like them. It's mostly cultural, I think.
It's just part of how people make connections and is normal, in my view.
Family references, names, etc. are about heritage much of the time, and that generally has some social connections that are important to people.