This isn't reddit, you know: the goal isn't to "punish" people for saying something "really, really wrong" (unless they're being uncivil or trolling, or other antisocial things). The idea is just to point out that they're wrong and move on. Think of it as a community, rather than just a random aggregation of strangers: when you tell a friend that they've done something wrong, you do it once, more or less gently, and then get on with things.

The "let's pile on to the guy who was wrong" mentality is a bit too much of a an unfriendly herd instinct for my tastes.