I'd say this: "We're a nice little community that is usually civil... but if you're used to a very lawful board you may be in for a shock. We've grown so used to each other that we seem to ignore rules most of the time. Topics veer off topic, sometimes with very little discussion of the actual topic done. We swear when we're not supposed to. We pretty much ignore six of our rules on a regular basis. This is mostly not a problem since we usually all tolerate it and there are no consequences. Problems tend to arise when new users expecting a perfectly lawful environment arrive.
Basically, we're good for the most part but you may see sides to us you don't like. Fortunately, if you're unable to take this in your stride, Recurring Villain is likely to either scare you away for force you to adapt. He's like our security guard."
Maybe not the best thing to say but that's what I'd say.
