You're assuming that because someone has made mistakes themselves they will judge others less harshly.

Actually, I don't think that's the only or most important factor. People who learn about the skeletons in your closet will compare you, not only to themselves, but to other people. If everyone has skeletons in their closet and everyone knows about them, then your prospective employer Bob (say) will be comparing the skeletons in your closet not only to the skeletons in his own closet, but more importantly to the skeletons in the closets of the other people who are competing with you for the same job.

As for people not making equal mistakes, to put it in simple binary terms merely for the purpose of making the point, divide people into "major offenders" and "minor offenders" and suppose major offenders are all equally major and minor all equally minor. If major offenders outnumber minor offenders, then being a major offender is not such a big deal since you're part of the majority. But if minor offenders outnumber major offenders, then only a minority of people will be major offenders and therefore only a minority will have to worry about a transparent society. So either way, the transparent society is not that big a thing to fear for the average person. It's a self-limiting danger. The more probable it is that the average person will be revealed to have Pervert Type A, the greater the fraction of people who will be revealed to be Pervert Type A, and therefore the harder it will be for other people to ostracize them, since to do so would reduce the size of their own social network.