In response to
"She honestly could not see that this was a complete contradiction of what she had said in the morning"
I'm sorry, but I do not see it either. May you please clarify? Thank you! 
Personally, I do see this as a contradiction. I understand the point that "All members of X group are Y" is a stereotype, while "The culture of X group indicates Y is not rude" is different. However, if those of us who are not in group X actually DO anything about a tendency (whether stereotypical, culturally influenced, etc) for Y, we are often guilty of prejudicial actions.
In the time example: "All FLS are rude and come to storytime late" is obviously untrue. "FLS culture doesn't emphasize being on time" may also be true, although it would be awfully presumptuous for someone who isn't FLS to say it. However, if the library staff (who are primarily not FLS) choose to actually DO something based on "FLS people come late", they are opening themselves up for a host of problems and accusations. A storytime aimed for FLS people that always starts half an hour after it says it will? That's prejudice, based on the "All FLS are rude and come to storytime late" stereotype! How dare you! Why can't you just treat FLS people like your other patrons! Etc. etc. etc.
I've got a frustrating problem in my library that highlights a number of the issues in this thread. My supervisor (at the main library) and I are white; my boss (the mayor of the small town my branch is in) and 97% of the town residents are black. My supervisor feels it's necessary for me to buy lots of children's books with black characters in them, and to forgive nearly all the fines accrued here, and to never take issue with parents who use the library as a free babysitting service, because "it's just part of the culture." While it MAY be true that black children prefer to read books with pictures of black characters, I feel it is racist to only buy those books at the expense of other great children's literature. Similarly, even though the "culture" here tends toward single parents who do a poor job of raising their children (my assessment), I take issue with having to babysit unattended kids because "it's just what they do down there."
Saying "In the black culture it is not a social stigma to be a single mother, therefore there are a number of single mothers who rely on the library as a safe place for their children while they work or do errands" still feels racist to me, even couched in positive terms, because we don't even feel the need to make that statement for white mothers. It's like you're a "mom" or a "black mom" or a "black single mom," but white single moms are still just a "mom" (no modifiers attatched). Actually acting on this idea (by ignoring the library policies on unattended minors in this branch while enforcing them elsewhere) feels even more racist.
I finally did get a policy changed - every other library branch would get noticed mailed four times a year to people who had accrued fines during those three months, or who had long-overdue materials. Except my branch. Apparently "If we mail out fine notices, a number of the parents will forbid their children to go to the library, and we don't want to deprive the children of the opportunity to learn. So just get whatever materials back that you can, but don't bring up fines." After finding that there were 40 movies that were just flat-out never returned over the last two years (oh, by the way, my annual movie budget covers about 40 movies, so that is over 50%), I got permission to have our fine notices mailed out too. What a great policy - "We don't think they'll be good parents, so let's not tell them when their kids take home books and movies and never bring them back."
Bah, turned into a rant, but this is something I'm particularly sensitive to. My supervisor is a bit racist (in a "but it's their CULTURE so we need to do everything different!" kind of way), and my boss the mayor is the one with her head screwed on straight.
