"I enjoy Slate's to-the-point contrarian attitude...."
--Me, too. Although I hate to be participating in what seems to be a periodic exercise in "yank the reader's chain."
--In addition to your excellent points, I was thinking about how this might work in real life:
I'm a parent of young children. I come across an old article that Joe Schmoe, my neighbor, is a pedophile. I cannot verify his identity on my local law enforcement pedophile web site. Yeah, he seems like a nice guy, but pedophiles often are, at least that's what the press tells me. Can't be too careful; my kids are involved. I screw up the nerve to approach Joe Schmoe (and make no mistake, most people wouldn't even bother). I raise the difficult subject. Joe Schmoe of course is upset and denies it; may even threaten me because, although I'm being a prudent parent, I'm also an effing jerk. Am I going to take his denial as proof? Of course not. If his friends vouch for him, will that be convincing? Absolutely not. Who's going to admit his friend is a pedophile? Short of an all-states criminal background check, which I have absolutely no right or power to demand, my children are not going anywhere near that man.
--On the less dramatic, but equally important issue of employment decisions, many places won't even get back to applicants with a formal rejection, much less tell them why they were not chosen. It's not inconceivable that a person's career could be ruined based on a false information of which s/he was unaware or unable to counter.
--In addition, this kind of comment is particularly callous coming from a journalist because: 1) journalists are in a better position to defend themselves against false rumors; 2) journalists enjoy the benefit of the double standard from other journalists.
--Mr. Shafer, it's time to rejoin the real world and accept that most people do not think and act like journalists, the scrupulously careful ones, that is. They aren't paid to spend their days checking things out. As I said before, they're busy, or lazy, or gullible, or just plain stupid, some are even willfully malicious.