Why would anonymity be important to you on a private message board?
Some union enthusiasts are rather emotional about differences of opinion. Being stuck with one of those guys in the cockpit for a tour would be unpleasant. Conversations on message boards can be more frank and honest and informative if we don't have to worry about reprisals for having a different opinion from the more vocal members of the herd.
I remember my favorite post from an antagonist here on Flightinfo who said, " I bet you would not say these things on a non-anonymous board!" Or words to that effect. My answer was, "You are absolutely right, and you are making my point."