The problem with "you know it when you see it", even in tight-knit communities, is that it's used to shut down discussion: If you know it when you see it, then

The problem with "you know it when you see it", even in tight-knit communities, is that it's used to shut down discussion: If you know it when you see it, then it's obvious, and if you're trying to argue the point, well, only a troll argues the obvious, innit? Nobody could disagree in good faith, so the only conclusion is that you're trying to make trouble and should be shut down. It's logically indefensible, in that there isn't enough to it to make a logical case to defend it, which means the people proposing ideas like these must believe that either their ideas are so widely shared that nobody would ever try to attack it, or that they'll be able to destroy anyone who does attack it through means other than calm, logical argumentation. That second possibility frightens me.