An eleventh commandment, as some might call it. But nay, this must not be so. For the warning in Matthew 7:1 is for those who wish to be the light and salt of our Lord to watch themselves, even more times than others, and keep themselves blameless. It is not "Thou shalt not judge", but "judge not, that ye be not judged"...expounded a few verses later in verse 5: ...first take the log out of your own eye, and then you will see clearly to take the speck out of your brother's eye.
However, as for those who wish to turn this into a taboo, I must question their motive. Is it because they wish not be embarrassed by anyone of their own mistakes so that they may continue living as sinners?
If we are at fault, nothing else matters except our own embarrassment and confession before our Lord (1Peter 2:20). Let God deal with the sins of the accusers, it is not our business to counter-judge when we ourselves need to repent (1Corinthians 6:7).