During presidential elections, polling agencies conduct polls with samples in the thousands of people range, sometimes 5000 or 10000 if it is a good survey and can determine the percentage each candidate has, +/- 4% is usually the standard deviation at 95% confidence level. I'm not sure if you thought they were polling all 400 million Americans, but I assure you they are not. A sample size is like dipping your spoon into your soup. You will likely pull out most of the ingredients and be able to come to some conclusions.
So I completely reject your premise that the AH bbs does not represent an appropriate and directly measurable sample size of the entire AH Community's sentiment. If 75% of the BBS users are against the 12 hr rule, then I assure you the actual population percentage against it are in the same ballpark. Could be 70% could be 80%, but it's in the ballpark.
I'm afraid I have to disagree.
Those polls are usually conducted by polling a representative section of the population or voters. When doing exit polls, the polling stations are carefully selected based on former election results to ensure as much as possible they are as representative as possible.
The AH BBS is a place where you have to sign up and to invest time to contribute. That alone already limits in some way the kind of players you usually encounter here with very active 'furballing' vet possibly overly represented. On top of that, a place like this one easily has some kind of "AH-political climate" (don't know to express this better in English) that may actually prevent many players of largely (perceived) deviating opinions (or adherents of deviating gaming styles) to spend their time and efforts here at all.
So it's probably more like readers of a specific magazine or newspaper, or the patrons of a certain bar or pub you are polling. Most probably not representative for the entirety of the public/voters at all.
One example coming to my mind are the plane polls of the past, As far as I remember, the real outcomes were quite different from the votes and opinions voiced here the AH BBS community. The B-29 would never had won the vote on the BBS.