Rebuke in the presence of all.

But wait a minute.  Wouldn't that require a judgment?  To decide if they are sinning or not?  :)

1 Timothy 5:20(NKJV)

20Those who are sinning rebuke in the presence of all, that the rest also may fear.

Just another example that the command "thou shalt not judge" is not the final word in the matter. 

Don't let those who know a little Scripture here and there mislead you.  We are charged by God to know our Scripture well enough so that doesn't happen.