well, within a culture people don't really talk about their own culture's specifice features because everyday-culture is made of what's "normal" to people and thus something they don't have to really think about. cultural habits and group behaviours is something that runs very subconsciously. people just "know" how to behave and how not to. anyway, from an U.S. american point of view it is true that there is a stronger insider-outsider consciousness than in the U.S. or let's say than in anglo-saxon influenced cultures in general. for example among americans and british people it's very common to start an easy conversation to strangers in bars or in other public areas. this concept of small talk is not really common in germany. in germany you usually stick to your own group of friends while going out. new people joining a fixed group are usually introduced by one of the group who already knows the "new" person. if a complete stranger persistently tries to enter a group by trying to start a conversation we would suspect that he or she is specifically interested in someone within the group or that it's a desperate person without any friends. an american friend of mine once told me that on an event he just asked to join a group at a table because he didn't have a place to put his glass. the people standing around the table actually stopped their conversation for a few awkward moments and then picked it up again completely ignoring my friend. There's a reason why there's expressions like "jetzt sind wir ja unter uns" ("we're among ourselves now"...so we can talk freely) and why it's quite important if someone says "ach, seid du und er jetzt schon per du?" ("oh, so you guys are already using "Du"?"). ah common misunderstanding between americans and germans is also the meaning of being friends. while being friends in the U.S. may just mean a loose connection which can be limited to just sharing a common activity in one's spare time, calling somone a real friend in germany usually means that you can depend on that person when you're in need of help and can share you're worries and problems with them. thus often germans are disappointed by american's behaviour who claimed to be their friends which leads to the misconception of americans being superficial, while many americans might feel to much pressure on them when being made a german's friend ;)

anyway, i just wanted to add that german's insider-outsider consciousness is not as strict as it may seem. there are lots of easy ways to enter one or several german "Freundeskreise". going to campus parties or knowing the bars were mostly students go helps a lot. generally no matter if you work or study in germany someone will usually sooner or later ask you to join their group for a drink or such and before you know it you're an "insider" yourself. a book that might interest you (if you don't already know it) is "germany unravelling an enigma" by Greg Nees. I read it and thought it described germans to americans in a very ballanced way. hope i could be of help to you

By cultural themes, I mean like social etiquette. For example, private space is highly valued in some cultures. Sorry for any confusion.

I'm not exactly sure what you mean by "insider vs. outside ideology", and by "cultural themes being stressed in social situations". Like everywhere, there certainly are some people in Germany who like to show off and sort of want to impress you with how educated they are, but that depends of course on the person. In everyday social situations, you rarely talk about "cultural themes". OTOH, if, say, I'm with a friend, and this friend knows I'm interested in literature, she could recommend some book to me she read recently. Or tell me about some interesting concert she went to. Or whatever. I'm don't know if this answers your question. Maybe you could add some more details?