Love them or hate them - CEG is the way it is primarily because of the
Forum Rules set in place (IMO, particularly rules 2, 4, and 6). They set a standard and maturity level that everyone is expected to follow. The moderators can't catch everything, but are certainly effective in keeping most people in line as well.
You'll notice this especially because the same people post between CEG and subforum-sites like ChicagoCEG. The way they act however on each site is dependent largely on the rules set in place or general standards.